devel/glib20 build issue

[Kristof Provost]

Hi,

While trying to build assorted ports on RISC-V I found that devel/glib20 
doesn’t build.
It turns out to be due to a missing __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 
define. That define is implicitly set by the toolchain. Or, at least, it 
is on other platforms (ARM, MIPS, x86, …), but not on RISC-V.

That’s likely just been forgotten. The following toolchain patch fixes 
that for me:

	diff --git a/contrib/llvm-project/clang/lib/Basic/Targets/RISCV.cpp 
b/contrib/llvm-project/clang/lib/Basic/Targets/RISCV.cpp
	index 4ba703c8dd1..73f1b5bc446 100644
	--- a/contrib/llvm-project/clang/lib/Basic/Targets/RISCV.cpp
	+++ b/contrib/llvm-project/clang/lib/Basic/Targets/RISCV.cpp
	@@ -115,8 +115,14 @@ void RISCVTargetInfo::getTargetDefines(const 
LangOptions &Opts,
	     Builder.defineMacro("__riscv_muldiv");
	   }

	-  if (HasA)
	+  if (HasA) {
	     Builder.defineMacro("__riscv_atomic");
	+    Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_1");
	+    Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2");
	+    Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4");
	+    if (Is64Bit)
	+           Builder.defineMacro("__GCC_HAVE_SYNC_COMPARE_AND_SWAP_8");
	+  }

	   if (HasF || HasD) {
	     Builder.defineMacro("__riscv_flen", HasD ? "64" : "32");

Best regards,
Kristof