[libunwind] Treat assembly files as C on mingw
When targeting mingw, current CMake (3.16) fails to get the right
flags for assembly source files for windows gnu/clang targets
(see https://gitlab.kitware.com/cmake/cmake/merge_requests/4287
for a fix), causing builds to fail due to `-fPIC` being unsupported
in clang for mingw targets
In the meantime, restore the behaviour from before c48974ffd7d1676
selectively on mingw targets, treating the assembly files as C.
Differential Revision: https://reviews.llvm.org/D73436
GitOrigin-RevId: b780df052dd2b246a760d00e00f7de9ebdab9d09
1 file changed
