Tracking issue for unconditionally ignored C tests.

[vext01]

There are quite a few unconditionally ignored C tests that fail for varying reasons. This issue tracks them.

crashes trace builder in handle_operand()

• funcptrarg_hasir.c
• indirect_external_function_call.c
• qsort.c

designed to test LLVM constant GEP expressions , but -O0 doesn't emit such code.

• constexpr.c

crashes ykllvm's BlockDisambiguate pass.

• indirect_branch.c:

not yet implemented: Unimplemented { tyidx: TyIdx(6), llvm_inst_str: " call void @llvm.memcpy.p0

• intrinsic_noinline.c

shadow stack can't do threads

• many_threads_many_locs.c
• many_threads_one_loc.c
• stats2.c

trace builder can't handle unmappable code "calling back" to mappable code.

• reentrant.c

not yet implemented: ran out of gp regs

• smmultisrc.c
• smmultisrc2.c

Crashes on unimplemented setjmp instruction

• stats3.c

doesn't trigger expected "trace too long"

• trace_too_long.c

Truncation currently always truncates to i32, no matter the target type

(maybe this is OK and we can delete/ammend the test without functional changes?)

• truncate.c

trace-compilation-aborted: dlsym("llvm.va_start") returned NULL

• varargs_inlined.c