Move toolchain utils to -toolchain package

Move LLVM ar, nm, and size.  Also move elftoolchain strings, which
should have already been there.

The remaining LLVM utilities (including strings) stay in -clang for now
since they're links to other executables.

Reviewed by:	des, dim
Differential Revision:	https://reviews.freebsd.org/D51583

usr.bin/clang/clang.prog.mk

@@ -31,7 +31,7 @@ DPADD+=		${OBJTOP}/lib/clang/lib${lib}/lib${LIBPRIV}${lib}.${LIBEXT}
 LDADD+=		${OBJTOP}/lib/clang/lib${lib}/lib${LIBPRIV}${lib}.${LIBEXT}
 .endfor
 
-PACKAGE=	clang
+PACKAGE?=	clang
 
 .if ${.MAKE.OS} == "FreeBSD" || !defined(BOOTSTRAPPING)
 LIBADD+=	execinfo

usr.bin/clang/llvm-ar/Makefile

@@ -1,5 +1,6 @@
 .include <src.opts.mk>
 
+PACKAGE=	toolchain
 PROG_CXX=	llvm-ar
 MAN=		llvm-ar.1 llvm-ranlib.1
 

usr.bin/clang/llvm-nm/Makefile

@@ -1,5 +1,6 @@
 .include <src.opts.mk>
 
+PACKAGE=	toolchain
 PROG_CXX=	llvm-nm
 
 SRCDIR=		llvm/tools/llvm-nm

usr.bin/clang/llvm-size/Makefile

@@ -1,5 +1,6 @@
 .include <src.opts.mk>
 
+PACKAGE=	toolchain
 PROG_CXX=	llvm-size
 
 SRCDIR=		llvm/tools/llvm-size

usr.bin/clang/llvm.prog.mk

@@ -25,7 +25,7 @@ DPADD+=		${OBJTOP}/lib/clang/lib${lib}/lib${LIBPRIV}${lib}.${LIBEXT}
 LDADD+=		${OBJTOP}/lib/clang/lib${lib}/lib${LIBPRIV}${lib}.${LIBEXT}
 .endfor
 
-PACKAGE=	clang
+PACKAGE?=	clang
 
 .if ${.MAKE.OS} == "FreeBSD" || !defined(BOOTSTRAPPING)
 LIBADD+=	execinfo

usr.bin/strings/Makefile

@@ -1,5 +1,7 @@
 .include <src.opts.mk>
 
+PACKAGE=	toolchain
+
 ELFTCDIR=	${SRCTOP}/contrib/elftoolchain
 
 .PATH: ${ELFTCDIR}/strings