Prefer MK_SSP=no to SSP_CFLAGS=

It is more idiomatic. CFLAGS is only augmented with $SSP_CFLAGS when
$MK_SSP != "no".

Reviewed by:	imp
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D31401

Makefile.inc1

@@ -714,7 +714,6 @@ BSARGS= 	DESTDIR= \
 		MAKEOBJDIRPREFIX= \
 		BOOTSTRAPPING=${BOOTSTRAPPING_OSRELDATE} \
 		BWPHASE=${.TARGET:C,^_,,} \
-		SSP_CFLAGS= \
 		-DNO_CPU_CFLAGS \
 		-DNO_LINT \
 		-DNO_PIC \
@@ -729,6 +728,7 @@ BSARGS= 	DESTDIR= \
 		MK_MAN=no \
 		MK_PROFILE=no \
 		MK_RETPOLINE=no \
+		MK_SSP=no \
 		MK_TESTS=no \
 		MK_UBSAN=no \
 		MK_WERROR=no \
@@ -749,7 +749,6 @@ TMAKE=		\
 		DESTDIR= \
 		BOOTSTRAPPING=${BOOTSTRAPPING_OSRELDATE} \
 		BWPHASE=${.TARGET:C,^_,,} \
-		SSP_CFLAGS= \
 		-DNO_CPU_CFLAGS \
 		-DNO_LINT \
 		MK_ASAN=no \
@@ -759,6 +758,7 @@ TMAKE=		\
 		MK_CLANG_FULL=no \
 		MK_LLDB=no \
 		MK_RETPOLINE=no \
+		MK_SSP=no \
 		MK_TESTS=no \
 		MK_UBSAN=no \
 		MK_WERROR=no
@@ -784,7 +784,6 @@ KTMAKE=		${TIME_ENV} \
 		OBJROOT='$${OBJTOP}/' \
 		MAKEOBJDIRPREFIX= \
 		BOOTSTRAPPING=${BOOTSTRAPPING_OSRELDATE} \
-		SSP_CFLAGS= \
 		-DNO_CPU_CFLAGS \
 		-DNO_LINT \
 		-DNO_PIC \
@@ -793,6 +792,7 @@ KTMAKE=		${TIME_ENV} \
 		MK_HTML=no \
 		MK_MAN=no \
 		MK_PROFILE=no \
+		MK_SSP=no \
 		MK_RETPOLINE=no \
 		MK_WERROR=no
 
@@ -2768,7 +2768,6 @@ NXBMAKEARGS+= \
 	-DNO_SHARED \
 	-DNO_CPU_CFLAGS \
 	-DNO_PIC \
-	SSP_CFLAGS= \
 	MK_CASPER=no \
 	MK_CLANG_EXTRAS=no \
 	MK_CLANG_FORMAT=no \
@@ -2784,6 +2783,7 @@ NXBMAKEARGS+= \
 	MK_PROFILE=no \
 	MK_RETPOLINE=no \
 	MK_SENDMAIL=no \
+	MK_SSP=no \
 	MK_TESTS=no \
 	MK_WERROR=no \
 	MK_ZFS=no

Makefile.libcompat

@@ -99,7 +99,7 @@ build${libcompat}: .PHONY
 	${_+_}cd ${.CURDIR}/${_dir}; \
 	    WORLDTMP=${WORLDTMP} \
 	    MAKEFLAGS="-m ${.CURDIR}/tools/build/mk ${.MAKEFLAGS}" \
-	    ${MAKE} SSP_CFLAGS= DESTDIR= \
+	    ${MAKE} DESTDIR= \
 	    OBJTOP=${LIBCOMPAT_OBJTOP} \
 	    OBJROOT='$${OBJTOP}/' \
 	    MAKEOBJDIRPREFIX= \
@@ -109,6 +109,7 @@ build${libcompat}: .PHONY
 	    MK_ASAN=no \
 	    MK_CTF=no \
 	    MK_RETPOLINE=no \
+	    MK_SSP=no \
 	    MK_UBSAN=no \
 	    MK_WERROR=no \
 	    ${_t}

lib/csu/Makefile.inc

@@ -1,13 +1,12 @@
 # $FreeBSD$
 
-SSP_CFLAGS=
-
 NO_WMISSING_VARIABLE_DECLARATIONS=
 # Can't instrument these files since that breaks non-sanitized programs.
 MK_ASAN:=	no
 MK_UBSAN:=	no
 
 .include <src.opts.mk>
+MK_SSP=	no
 
 .if !defined(BUILDING_TESTS)
 

lib/libclang_rt/Makefile.inc

@@ -13,11 +13,11 @@ SHLIBDIR=	${LIBDIR}
 NO_PIC=
 MK_PROFILE=	no
 MK_ASAN:=	no
+MK_SSP=		no
 MK_UBSAN:=	no
 
 WARNS?=		0
 
-SSP_CFLAGS=
 CFLAGS+=	-DNDEBUG
 CFLAGS+=	-DHAVE_RPC_XDR_H=0
 CFLAGS+=	-DSANITIZER_SUPPORTS_WEAK_HOOKS=0

stand/defs.mk

@@ -135,8 +135,6 @@ LD_FLAGS+=	-m elf_i386_fbsd
 AFLAGS+=	--32
 .endif
 
-SSP_CFLAGS=
-
 # Add in the no float / no SIMD stuff and announce we're freestanding
 # aarch64 and riscv don't have -msoft-float, but all others do.
 CFLAGS+=	-ffreestanding ${CFLAGS_NO_SIMD}

targets/pseudo/bootstrap-tools/Makefile

@@ -39,7 +39,6 @@ BSARGS= 	DESTDIR= \
 		MAKEOBJDIRPREFIX= \
 		BOOTSTRAPPING=${OSRELDATE} \
 		BWPHASE=${.TARGET} \
-		SSP_CFLAGS= \
 		-DNO_CPU_CFLAGS \
 		-DNO_LINT \
 		-DNO_PIC \
@@ -53,6 +52,7 @@ BSARGS= 	DESTDIR= \
 		MK_MAN=no \
 		MK_PROFILE=no \
 		MK_RETPOLINE=no \
+		MK_SSP=no \
 		MK_TESTS=no \
 		MK_WERROR=no \
 		MK_INCLUDES=yes \