build llvm-ar and llvm-nm with Clang (promote out of CLANG_EXTRAS)

To facilitate experimentation with LTO we require an ar that supports
LLVM IR, and to a lesser degree also an nm.  As a first step always
install llvm-ar and llvm-nm.

Sponsored by:	The FreeBSD Foundation

lib/clang/libllvm/Makefile

@@ -718,8 +718,8 @@ SRCS_EXT+=	MCA/Support.cpp
 SRCS_MIN+=	Object/Archive.cpp
 SRCS_MIN+=	Object/ArchiveWriter.cpp
 SRCS_MIN+=	Object/Binary.cpp
-SRCS_EXT+=	Object/COFFImportFile.cpp
-SRCS_EXT+=	Object/COFFModuleDefinition.cpp
+SRCS_MIN+=	Object/COFFImportFile.cpp
+SRCS_MIN+=	Object/COFFModuleDefinition.cpp
 SRCS_MIN+=	Object/COFFObjectFile.cpp
 SRCS_MIN+=	Object/Decompressor.cpp
 SRCS_MIN+=	Object/ELF.cpp
@@ -1256,7 +1256,7 @@ SRCS_MIN+=	Target/X86/X86VZeroUpper.cpp
 SRCS_MIN+=	Target/X86/X86WinAllocaExpander.cpp
 SRCS_MIN+=	Target/X86/X86WinEHState.cpp
 .endif # MK_LLVM_TARGET_X86
-SRCS_EXT+=	ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
+SRCS_MIN+=	ToolDrivers/llvm-dlltool/DlltoolDriver.cpp
 SRCS_EXL+=	ToolDrivers/llvm-lib/LibDriver.cpp
 SRCS_MIN+=	Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
 SRCS_MIN+=	Transforms/AggressiveInstCombine/TruncInstCombine.cpp

usr.bin/clang/Makefile

@@ -7,6 +7,8 @@ SUBDIR+=	clang-tblgen
 SUBDIR+=	llvm-tblgen
 
 .if !defined(TOOLS_PREFIX)
+SUBDIR+=	llvm-ar
+SUBDIR+=	llvm-nm
 SUBDIR+=	llvm-objdump
 SUBDIR+=	llvm-symbolizer
 
@@ -15,7 +17,6 @@ SUBDIR+=	bugpoint
 SUBDIR+=	clang-format
 SUBDIR+=	llc
 SUBDIR+=	lli
-SUBDIR+=	llvm-ar
 SUBDIR+=	llvm-as
 SUBDIR+=	llvm-bcanalyzer
 SUBDIR+=	llvm-cxxdump
@@ -30,7 +31,6 @@ SUBDIR+=	llvm-lto2
 SUBDIR+=	llvm-mc
 SUBDIR+=	llvm-mca
 SUBDIR+=	llvm-modextract
-SUBDIR+=	llvm-nm
 SUBDIR+=	llvm-objcopy
 SUBDIR+=	llvm-pdbutil
 SUBDIR+=	llvm-rtdyld