llvm-cxxfilt: Install as c++filt only with LLVM_BINUTILS

When building WITHOUT_LLVM_BINUTILS /usr/bin/c++filt is the one from
ELF Tool Chain.

PR: 293610
Fixes: 5d757312ad ("build: Retire LLVM_CXXFILT option")
Sponsored by: The FreeBSD Foundation

usr.bin/clang/llvm-cxxfilt/Makefile

@@ -22,7 +22,9 @@ DEPENDFILES+=	${TGHDRS:C/$/.d/}
 DPSRCS+=	${TGHDRS}
 CLEANFILES+=	${TGHDRS} ${TGHDRS:C/$/.d/}
 
+.if ${MK_LLVM_BINUTILS} != "no"
 LINKS=		${BINDIR}/llvm-cxxfilt ${BINDIR}/c++filt
 MLINKS=		llvm-cxxfilt.1 c++filt.1
+.endif
 
 .include "../llvm.prog.mk"