[compiler-rt][asan][test] Skipt sanitizer_common tests on Sparc

When building on `sparc64-unknown-linux-gnu`, I found that a large number
of `SanitizerCommon-asan-sparc*-Linux` tests were `FAIL`ing, like

   SanitizerCommon-asan-sparc-Linux :: Linux/aligned_alloc-alignment.cpp
  [...]
   SanitizerCommon-asan-sparcv9-Linux :: Linux/aligned_alloc-alignment.cpp
  [...]

many of them due to

  fatal error: error in backend: Function "_Z14User_OnSIGSEGViP9siginfo_tPv": over-aligned dynamic alloca not supported.

which breaks ASan on Sparc.  Currently ASan is only built for the benefit
of `gcc` where it does work.  However, when enabling the compilation in
`compiler-rt` to make certain it continues to build, I missed
`compiler-rt/test/sanitizer_common` when disabling ASan testing on Sparc
(it's not yet enabled on Solaris).

This patch fixes the issue.

Tested on `sparcv9-sun-solaris2.11` with the `sanitizer_comon` testsuite enabled.

Differential Revision: https://reviews.llvm.org/D85732