usr.bin/Makefile: always build ELF Tool Chain strings(1)

strings(1) is not conditional on WITH_/WITHOUT_TOOLCHAIN, as it is a
small utility that is also useful outside of the toolchain context.
As of commit 1cae712 we switched to WITH_LLVM_BINUTILS by default.

After this change building world with default options but installing
WITHOUT_TOOLCHAIN failed, because we would build LLVM's strings but
attempt to install ELF Tool Chain's version, which did not exist.
Address this by always including ELF Tool Chain strings in non-install
make targets, so that it will be available if options are changed at
install time.

PR:		285556
Reported by:	Michael Butler
Reviewed by:	brooks
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D49425

Author: emaste

usr.bin/Makefile

@@ -250,6 +250,12 @@ SUBDIR.${MK_TOOLCHAIN}+=	nm
 SUBDIR.${MK_TOOLCHAIN}+=	objcopy
 SUBDIR.${MK_TOOLCHAIN}+=	readelf
 SUBDIR.${MK_TOOLCHAIN}+=	size
+.endif
+# Include elftoolchain's strings in build targets even if using LLVM_BINUTILS,
+# as we may later install with different options.  In particular, the release
+# artifact builds use default options for buildworld but install with
+# MK_TOOLCHAIN=no which implies MK_LLVM_BINUTILS=no.
+.if ${MK_LLVM_BINUTILS} == "no" || !make(install)
 SUBDIR+=			strings
 .endif
 SUBDIR.${MK_TOOLCHAIN}+=	c89