unwind: improve compilation on Linux with gcc

gcc still defaults to C89 which does not support BCPL style comments.  This
splits up the sources list in CMakeLists and selectively adds compile flags for
using C99 which avoids a number of warnings in -Wpedantic mode.  NFC.

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@228665 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed