diff --git a/Makefile.inc1 b/Makefile.inc1
index 592cddaff564..c15a2bad7bd5 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -1226,7 +1226,9 @@ _awk=		usr.bin/awk
 _gensnmptree=	usr.sbin/bsnmpd/gensnmptree
 .endif
 
-.if ${MK_CLANG_IS_CC} != "no" || ${CC:T:Mclang} == "clang" || ${MK_CLANG} != "no"
+# We need to build tlbgen when we're building clang either as
+# the bootstrap compiler, or as the part of the normal build.
+.if ${MK_CLANG_BOOTSTRAP} != "no" || ${MK_CLANG} != "no"
 _clang_tblgen= \
 	lib/clang/libllvmsupport \
 	lib/clang/libllvmtablegen \
@@ -1366,22 +1368,19 @@ _kgzip=		usr.sbin/kgzip
 .endif
 .endif
 
-.if ${XAS:M/*} == "" && ${MK_BINUTILS} != "no"
+# If we're given an XAS, don't build binutils.
+.if ${XAS:M/*} == "" && ${MK_BINUTILS_BOOTSTRAP} != "no"
 _binutils=	gnu/usr.bin/binutils
 .endif
 
 # If an full path to an external cross compiler is given, don't build
 # a cross compiler.
 .if ${XCC:M/*} == "" && ${MK_CROSS_COMPILER} != "no"
-.if ${MK_CLANG_IS_CC} != "no" || ${CC:T:Mclang} == "clang"
+.if ${MK_CLANG_BOOTSTRAP} != "no"
 _clang=		usr.bin/clang
 _clang_libs=	lib/clang
-.else
-_cc=		gnu/usr.bin/cc
 .endif
-
-# The boot2 for pc98 requires gcc.
-.if ${TARGET} == "pc98"
+.if ${MK_GCC_BOOTSTRAP} != "no"
 _cc=		gnu/usr.bin/cc
 .endif
 .endif
diff --git a/share/mk/bsd.own.mk b/share/mk/bsd.own.mk
index c3bf33b2f7a1..b2ce1005bc3e 100644
--- a/share/mk/bsd.own.mk
+++ b/share/mk/bsd.own.mk
@@ -237,6 +237,7 @@ __DEFAULT_YES_OPTIONS = \
     AUDIT \
     AUTHPF \
     BINUTILS \
+    BINUTILS_BOOTSTRAP \
     BLUETOOTH \
     BMAKE \
     BOOT \
@@ -387,13 +388,13 @@ __TT=${MACHINE}
 .endif
 # Clang is only for x86, powerpc and little-endian arm right now, by default.
 .if ${__T} == "amd64" || ${__T} == "i386" || ${__T:Mpowerpc*}
-__DEFAULT_YES_OPTIONS+=CLANG CLANG_FULL
+__DEFAULT_YES_OPTIONS+=CLANG CLANG_FULL CLANG_BOOTSTRAP
 .elif ${__T} == "arm" || ${__T} == "armv6" || ${__T} == "armv6hf"
-__DEFAULT_YES_OPTIONS+=CLANG
+__DEFAULT_YES_OPTIONS+=CLANG CLANG_BOOTSTRAP
 # GCC is unable to build the full clang on arm, disable it by default.
 __DEFAULT_NO_OPTIONS+=CLANG_FULL
 .else
-__DEFAULT_NO_OPTIONS+=CLANG CLANG_FULL
+__DEFAULT_NO_OPTIONS+=CLANG CLANG_FULL CLANG_BOOTSTRAP
 .endif
 # Clang the default system compiler only on little-endian arm and x86.
 .if ${__T} == "amd64" || ${__T} == "arm" || ${__T} == "armv6" || \
@@ -403,14 +404,14 @@ __DEFAULT_NO_OPTIONS+=GNUCXX
 # The pc98 bootloader requires gcc to build and so we must leave gcc enabled
 # for pc98 for now.
 .if ${__TT} == "pc98"
-__DEFAULT_YES_OPTIONS+=GCC
+__DEFAULT_YES_OPTIONS+=GCC GCC_BOOTSTRAP
 .else
-__DEFAULT_NO_OPTIONS+=GCC
+__DEFAULT_NO_OPTIONS+=GCC GCC_BOOTSTRAP
 .endif
 .else
 # If clang is not cc, then build gcc by default
-__DEFAULT_NO_OPTIONS+=CLANG_IS_CC
-__DEFAULT_YES_OPTIONS+=GCC GNUCXX
+__DEFAULT_NO_OPTIONS+=CLANG_IS_CC CLANG CLANG_BOOTSTRAP
+__DEFAULT_YES_OPTIONS+=GCC GNUCXX GCC_BOOTSTRAP
 .endif
 
 #
@@ -531,6 +532,12 @@ MK_AUTHPF:=	no
 MK_GROFF:=	no
 .endif
 
+.if ${MK_CROSS_COMPILER} == "no"
+MK_BINUTILS_BOOTSTRAP:= no
+MK_CLANG_BOOTSTRAP:= no
+MK_GCC_BOOTSTRAP:= no
+.endif
+
 .if ${MK_TOOLCHAIN} == "no"
 MK_BINUTILS:=	no
 MK_CLANG:=	no
diff --git a/tools/build/options/WITHOUT_BINUTILS b/tools/build/options/WITHOUT_BINUTILS
index 62a614e94d0e..5270bd7fd851 100644
--- a/tools/build/options/WITHOUT_BINUTILS
+++ b/tools/build/options/WITHOUT_BINUTILS
@@ -1,7 +1,7 @@
 .\" $FreeBSD$
-Set to not install binutils (as, c++-filt, gconv,
-ld, nm, objcopy, objdump, readelf, size and strip).
-.Bf -symbolic
-The option does not generally work for build targets, unless some alternative
-toolchain is enabled.
-.Ef
+Set to not build or install binutils (as, c++-filt, gconv,
+ld, nm, objcopy, objdump, readelf, size and strip) as part
+of the normal system build.
+The resulting system cannot build programs from source.
+
+
diff --git a/tools/build/options/WITHOUT_BINUTILS_BOOTSTRAP b/tools/build/options/WITHOUT_BINUTILS_BOOTSTRAP
new file mode 100644
index 000000000000..84ae1a1706f2
--- /dev/null
+++ b/tools/build/options/WITHOUT_BINUTILS_BOOTSTRAP
@@ -0,0 +1,8 @@
+.\" $FreeBSD$
+Set to not build binutils (as, c++-filt, gconv,
+ld, nm, objcopy, objdump, readelf, size and strip)
+as part of the bootstrap process.
+.Bf -symbolic
+The option does not work for build targets unless some alternative
+toolchain is provided.
+.Ef
diff --git a/tools/build/options/WITHOUT_CLANG b/tools/build/options/WITHOUT_CLANG
index 62a90bab215e..51c9c514e68b 100644
--- a/tools/build/options/WITHOUT_CLANG
+++ b/tools/build/options/WITHOUT_CLANG
@@ -1,2 +1,2 @@
 .\" $FreeBSD$
-Set to not build the Clang C/C++ compiler.
+Set to not build the Clang C/C++ compiler during the regular phase of the build.
diff --git a/tools/build/options/WITHOUT_CLANG_BOOTSTRAP b/tools/build/options/WITHOUT_CLANG_BOOTSTRAP
new file mode 100644
index 000000000000..a22046d19248
--- /dev/null
+++ b/tools/build/options/WITHOUT_CLANG_BOOTSTRAP
@@ -0,0 +1,5 @@
+.\" $FreeBSD$
+Set to not build the Clang C/C++ compiler during the bootstrap phase of the build.
+You must enable wither gcc or clang bootstrap to be able to build the system,
+unless an alternative compiiler is provided via
+XCC.
diff --git a/tools/build/options/WITHOUT_CROSS_COMPILER b/tools/build/options/WITHOUT_CROSS_COMPILER
index 1ded25b06573..ab1bd235bb05 100644
--- a/tools/build/options/WITHOUT_CROSS_COMPILER
+++ b/tools/build/options/WITHOUT_CROSS_COMPILER
@@ -1,3 +1,13 @@
 .\" $FreeBSD$
-Set to not build a cross compiler in the cross-tools stage of
-buildworld, buildkernel, etc.
+Set to not build any cross compiler in the cross-tools stage of buildworld.
+If you are compiling a different version of
+.Fx 
+than what is installed on the system, you will need to provide an alternate
+compiler with XCC to ensure success.
+If you are compiling with an identical version of
+.Fx 
+to the host, this option may be safely used.
+This option may also be safe when the host version of
+.Fx 
+is close to the sources being built, but all bets are off if there have
+been any changes to the toolchain between the versions.
diff --git a/tools/build/options/WITHOUT_GCC b/tools/build/options/WITHOUT_GCC
index 7bb21f8b8375..c746d16dc076 100644
--- a/tools/build/options/WITHOUT_GCC
+++ b/tools/build/options/WITHOUT_GCC
@@ -1,2 +1,2 @@
 .\" $FreeBSD$
-Set to not build and install gcc and g++.
+Set to not build and install gcc and g++ as part of the normal build process.
diff --git a/tools/build/options/WITHOUT_GCC_BOOTSTRAP b/tools/build/options/WITHOUT_GCC_BOOTSTRAP
new file mode 100644
index 000000000000..668ff14496a0
--- /dev/null
+++ b/tools/build/options/WITHOUT_GCC_BOOTSTRAP
@@ -0,0 +1,5 @@
+.\" $FreeBSD$
+Set to not build gcc and g++ as part of the bootstrap process.
+You must enable wither gcc or clang bootstrap to be able to build the system,
+unless an alternative compiiler is provided via
+XCC.
diff --git a/tools/build/options/WITH_CLANG b/tools/build/options/WITH_CLANG
index b0e300a488b1..0174b4db4e38 100644
--- a/tools/build/options/WITH_CLANG
+++ b/tools/build/options/WITH_CLANG
@@ -1,2 +1,2 @@
 .\" $FreeBSD$
-Set to build the Clang C/C++ compiler.
+Set to build the Clang C/C++ compiler during the normal phase of the build.
diff --git a/tools/build/options/WITH_CLANG_BOOTSTRAP b/tools/build/options/WITH_CLANG_BOOTSTRAP
new file mode 100644
index 000000000000..792512d57e93
--- /dev/null
+++ b/tools/build/options/WITH_CLANG_BOOTSTRAP
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to build the Clang C/C++ compiler during the bootstrap phase of the build.
diff --git a/tools/build/options/WITH_GCC_BOOTSTRAP b/tools/build/options/WITH_GCC_BOOTSTRAP
new file mode 100644
index 000000000000..8e04b11fb483
--- /dev/null
+++ b/tools/build/options/WITH_GCC_BOOTSTRAP
@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to build gcc and g++ as part of the bootstrap process.