Add WITH_LLVM_CXXFILT option to install llvm-cxxfilt as c++filt

Since elftoolchain's cxxfilt is rather far behind on features, and we
ran into several bugs, add an option to use llvm-cxxfilt as an drop-in
replacement.

It supports the same options as elftoolchain cxxfilt, though it doesn't
have support for old ARM (C++ Annotated Reference Manual, not the CPU)
and GNU v2 manglings. But these are irrelevant in 2020.

Note: as we already compile the required libraries as part of libllvm,
this will not add any significant build time either.

PR:		250702
Reviewed by:	emaste, yuri
Differential Revision: https://reviews.freebsd.org/D27071
MFC after:	2 weeks

share/man/man5/src.conf.5

@@ -1,6 +1,6 @@
 .\" DO NOT EDIT-- this file is @generated by tools/build/options/makeman.
 .\" $FreeBSD$
-.Dd September 15, 2020
+.Dd November 3, 2020
 .Dt SRC.CONF 5
 .Os
 .Sh NAME
@@ -919,6 +919,8 @@ Set to disable debugging assertions in LLVM.
 Set to not build the
 .Xr llvm-cov 1
 tool.
+.It Va WITH_LLVM_CXXFILT
+Install LLVM's llvm-cxxfilt as c++filt, instead of ELF Tool Chain's cxxfilt.
 .It Va WITHOUT_LLVM_TARGET_AARCH64
 Set to not build LLVM target support for AArch64.
 The

share/mk/src.opts.mk

@@ -210,6 +210,7 @@ __DEFAULT_NO_OPTIONS = \
     GNU_GREP_COMPAT \
     HESIOD \
     LIBSOFT \
+    LLVM_CXXFILT \
     LOADER_FIREWIRE \
     LOADER_VERBOSE \
     LOADER_VERIEXEC_PASS_MANIFEST \

tools/build/options/WITHOUT_LLVM_CXXFILT

@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Install ELF Tool Chain's cxxfilt as c++filt, instead of LLVM's llvm-cxxfilt.

tools/build/options/WITH_LLVM_CXXFILT

@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Install LLVM's llvm-cxxfilt as c++filt, instead of ELF Tool Chain's cxxfilt.

usr.bin/Makefile

@@ -260,7 +260,9 @@ SUBDIR.${MK_TOOLCHAIN}+=	ar
 SUBDIR.${MK_TOOLCHAIN}+=	c89
 SUBDIR.${MK_TOOLCHAIN}+=	c99
 SUBDIR.${MK_TOOLCHAIN}+=	ctags
+.if ${MK_LLVM_CXXFILT} == "no"
 SUBDIR.${MK_TOOLCHAIN}+=	cxxfilt
+.endif
 SUBDIR.${MK_TOOLCHAIN}+=	objcopy
 SUBDIR.${MK_TOOLCHAIN}+=	file2c
 SUBDIR.${MK_TOOLCHAIN}+=	gprof

usr.bin/clang/Makefile

@@ -16,6 +16,10 @@ SUBDIR+=	llvm-nm
 SUBDIR+=	llvm-objdump
 SUBDIR+=	llvm-symbolizer
 
+.if ${MK_CLANG_EXTRAS} != "no" || ${MK_LLVM_CXXFILT} != "no"
+SUBDIR+=	llvm-cxxfilt
+.endif
+
 .if ${MK_CLANG_EXTRAS} != "no"
 SUBDIR+=	bugpoint
 SUBDIR+=	llc
@@ -23,7 +27,6 @@ SUBDIR+=	lli
 SUBDIR+=	llvm-as
 SUBDIR+=	llvm-bcanalyzer
 SUBDIR+=	llvm-cxxdump
-SUBDIR+=	llvm-cxxfilt
 SUBDIR+=	llvm-diff
 SUBDIR+=	llvm-dis
 SUBDIR+=	llvm-dwarfdump

usr.bin/clang/llvm-cxxfilt/Makefile

@@ -1,8 +1,15 @@
 # $FreeBSD$
 
+.include <src.opts.mk>
+
 PROG_CXX=	llvm-cxxfilt
 
 SRCDIR=		llvm/tools/llvm-cxxfilt
 SRCS+=		llvm-cxxfilt.cpp
 
+.if ${MK_LLVM_CXXFILT} != "no"
+LINKS=		${BINDIR}/llvm-cxxfilt ${BINDIR}/c++filt
+MLINKS=		llvm-cxxfilt.1 c++filt.1
+.endif
+
 .include "../llvm.prog.mk"