Backport fix profiler building with MinGW GCC

[mati865]

Differential Revision: https://reviews.llvm.org/D86405

[cuviper]

Can you also file an LLVM backport bug blocking release-11.0.0?

[mati865]

It's already very late for backports and this doesn't fix the issue entirely when building with GCC.

Thanks to this patch one can link to profiler library built by GCC without errors to check on the CI if binaries are properly instrumented.

But instrumented binary will crash like this:

Backtrace

Process 8324 launched: 'D:\Projekty\rust\build\x86_64-pc-windows-gnu\test\run-make-fulldeps\instrument-coverage\instrume
nt-coverage\testprog.exe' (x86_64)
Process 8324 stopped
* thread #1, stop reason = Exception 0xc0000005 encountered at address 0x1400ad4d0: Access violation reading location 0x
00000012
    frame #0: 0x00000001400ad4d0 testprog.exe`initializeValueProfRuntimeRecord(Data=0x00000001400e5030, SiteCountArray=0
x0000000000000000) at InstrProfilingValue.c:332:14
   329            Nodes ? RTRecord.NodesKind[I][J] : INSTR_PROF_NULLPTR;
   330        while (Site) {
   331          C++;
-> 332          Site = Site->Next;
   333        }
   334        if (C > UCHAR_MAX)
   335          C = UCHAR_MAX;
(lldb) bt
* thread #1, stop reason = Exception 0xc0000005 encountered at address 0x1400ad4d0: Access violation reading location 0x
00000012
  * frame #0: 0x00000001400ad4d0 testprog.exe`initializeValueProfRuntimeRecord(Data=0x00000001400e5030, SiteCountArray=0
x0000000000000000) at InstrProfilingValue.c:332:14
    frame #1: 0x00000001400af05e testprog.exe`writeOneValueProfData(VPDataReader=0x00000001400d8560, Data=0x00000001400e
5030, BufferIO=0x00000001400d8540) at InstrProfilingWriter.c:146:25
    frame #2: 0x00000001400ae2e4 testprog.exe`lprofWriteDataImpl at InstrProfilingWriter.c:227:9
    frame #3: 0x00000001400ae262 testprog.exe`lprofWriteDataImpl(Writer=0x000000000014fd70, DataBegin=<unavailable>, Dat
aEnd=0x00000001400e51c0, CountersBegin=0x00000001400e4008, CountersEnd=0x00000001400e4048, VPDataReader=0x00000001400d85
60, NamesBegin="", NamesEnd="", SkipNameDataWrite=0) at InstrProfilingWriter.c:299
    frame #4: 0x00000001400adfd0 testprog.exe`lprofWriteData(Writer=0x000000000014fd70, VPDataReader=0x00000001400d8560,
 SkipNameDataWrite=0) at InstrProfilingWriter.c:248:10
    frame #5: 0x00000001400ac373 testprog.exe`__llvm_profile_write_file at InstrProfilingFile.c:346:12
    frame #6: 0x00000001400ac223 testprog.exe`__llvm_profile_write_file at InstrProfilingFile.c:935

That single test worked fine with profiler build by Clang so I don't think there is much gain in blocking LLVM 11 release on it.