Reapply "Merge commit e24f90190c77 from llvm git (by Brad Smith):"

[Driver] Enable outline atomics for FreeBSD/aarch64 (#156089)

The compiler_rt helper functions have been built since 12.4, 13.1, 14
and anything newer.

This reverts commit bd27bd1f51.

Only some people (including the release manager, unfortunately) ran into
build issues with the previous iteration of this commit, because they
were bootstrapping the compiler, either via the WITHOUT_SYSTEM_COMPILER
src.conf(5) setting, or because the build system determined that their
base system compiler was out of date.

The bootstrapped compiler would then enable outline atomics and compile
libgcc_s with these, but because libgcc_s is linked with -nodefaultlibs,
it could not find the helper routines in libcompiler_rt.a.

In contrast, people who did not bootstrap the compiler never saw any
issues, because libgcc_s was built using their 'old' base system
compiler, and so libgcc_s would not contain any calls to those helper
routines.

Fix this by ensuring that libgcc_s is linked against libcompiler_rt.a
explicitly, similar to some other binaries and libraries that are built
with -nodefaultlibs.

Also, bump FREEBSD_CC_VERSION to ensure that everybody gets the updated
compiler with outline atomics enabled. (This should have been done in
the first iteration of this commit, because the error would have shown
up right away then.)

MFC after:	3 days

contrib/llvm-project/clang/lib/Driver/ToolChains/FreeBSD.h

@@ -78,6 +78,11 @@ public:
   void AddHIPIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                          llvm::opt::ArgStringList &CC1Args) const override;
 
+  bool IsAArch64OutlineAtomicsDefault(
+      const llvm::opt::ArgList &Args) const override {
+    return true;
+  }
+
   UnwindTableLevel
   getDefaultUnwindTableLevel(const llvm::opt::ArgList &Args) const override;
   bool isPIEDefault(const llvm::opt::ArgList &Args) const override;

lib/clang/freebsd_cc_version.h

@@ -1 +1 @@
-#define	FREEBSD_CC_VERSION 1600000
+#define	FREEBSD_CC_VERSION 1600001

lib/libgcc_s/Makefile

@@ -11,7 +11,9 @@ MK_SSP=		no
 WARNS?=	2
 
 LDFLAGS+=	-nodefaultlibs
+LDFLAGS+=	-Wl,-Bsymbolic
 LIBADD+=	c
+LIBADD+=	compiler_rt
 
 VERSION_DEF=	${.CURDIR}/Versions.def
 SYMBOL_MAPS=	${.CURDIR}/Symbol.map