debug info issues when linking libc on mingw

[emekoi]

when linking to libc on mingw-w64 lld places the pdb info in the .buildid rather than .rdata. this breaks stack traces and debug info parsing on mingw-w64. another possible interesting area of research is that lld seems to support outputting DWARF debug info for windows. perhaps for debug builds on windows we could try finding some way to output both types of debug info.

[emekoi]

the easiest workaround would appear to be removing this line, but i'm not sure if this introduces intended behavior. yep, lld can't link without it.

[andrewrk]

This is the code choosing CodeView instead of DWARF:

zig/src/codegen.cpp

Lines 8004 to 8008 in bc982e6

	if (target_object_format(g->zig_target) == ZigLLVM_COFF) {
	ZigLLVMAddModuleCodeViewFlag(g->module);
	} else {
	ZigLLVMAddModuleDebugInfoFlag(g->module);
	}

[Sahnvour]

Looking at why they do it this way, it's quite a special case llvm-mirror/lld@9722f66.

[andrewrk]

Would be happy to accept reasonable PRs for mingw compat but it is not one of the supported targets of Zig, so I don't want to have issues open for it.