Retire BINUTILS and BINUTILS_BOOTSTRAP options

As of r361857 all BINUTILS options are disabled by default - ports
have been changed to depend on binutils if they require GNU as, and
all base system assembly files have been switched to use Clang's
integrated assembler.

Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation

Makefile.inc1

@@ -300,7 +300,7 @@ TEST_SYSTEM_COMPILER_VARS= \
 	X_COMPILER_FREEBSD_VERSION
 TEST_SYSTEM_LINKER_VARS= \
 	USING_SYSTEM_LINKER MK_SYSTEM_LINKER \
-	MK_LLD_BOOTSTRAP MK_BINUTILS_BOOTSTRAP \
+	MK_LLD_BOOTSTRAP \
 	WANT_LINKER_TYPE WANT_LINKER_VERSION WANT_LINKER_VERSION_FILE \
 	WANT_LINKER_FREEBSD_VERSION WANT_LINKER_FREEBSD_VERSION_FILE \
 	LD LINKER_TYPE LINKER_FEATURES LINKER_VERSION \
@@ -2421,9 +2421,6 @@ _dtrace_tools= cddl/lib/libctf cddl/usr.bin/ctfconvert \
 
 # If we're given an XAS, don't build binutils.
 .if ${XAS:M/*} == ""
-.if ${MK_BINUTILS_BOOTSTRAP} != "no"
-_binutils=	gnu/usr.bin/binutils
-.endif
 .if ${MK_ELFTOOLCHAIN_BOOTSTRAP} != "no"
 _elftctools=	lib/libelftc \
 		lib/libpe \
@@ -2467,7 +2464,6 @@ cross-tools: .MAKE .PHONY
     ${_clang_libs} \
     ${_clang} \
     ${_lld} \
-    ${_binutils} \
     ${_elftctools} \
     ${_dtrace_tools} \
     ${_btxld} \
@@ -2565,9 +2561,6 @@ SUBDIR_DEPEND_usr.bin/clang=	lib/clang
 NXBDIRS+=	lib/clang
 NXBDIRS+=	usr.bin/clang
 .endif
-.if ${MK_BINUTILS} != "no"
-NXBDIRS+=	gnu/usr.bin/binutils
-.endif
 # XXX: native-xtools passes along ${NXBDIRS} in SUBDIR_OVERRIDE that needs
 # to be evaluated after NXBDIRS is set.
 .if make(install) && !empty(SUBDIR_OVERRIDE)
@@ -3273,7 +3266,6 @@ _xb-build-tools: .PHONY
 XDEVDIRS= \
     ${_clang_libs} \
     ${_lld} \
-    ${_binutils} \
     ${_elftctools} \
     usr.bin/ar \
     ${_clang}