[cfe-dev] disable unittest on specific targets (broken buildbots)

[Gábor Márton via cfe-dev]

Hi,

I have a commit which breaks a unittest (gtest and not a lit test) on
certain platforms/buildbots: clang-ppc64be-linux,
clang-x64-windows-msvc.
Those platforms do not support the calling conventions used in the test:
```
[==========] 1 test from 1 test case ran. (45 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] StructuralEquivalenceFunctionTest.FunctionsWithDifferentCallingConventions

 1 FAILED TEST
input.cc:1:16: warning: calling convention 'fastcall' ignored for this
target [-Wignored-attributes]
__attribute__((fastcall)) void foo();
               ^
input.cc:1:16: warning: calling convention 'ms_abi' ignored for this
target [-Wignored-attributes]
__attribute__((ms_abi))   void foo();
               ^
```

Is there a way to disable a unittest on these platforms?
I am thinking about #ifndef ppc and #ifndef windows ... is there such
defines available?

Many thanks,
Gabor