syntheticpp/ninja — comment on commit a25bb24b57443c1d0aee613ee2a97307e9a9679a
File: misc/CMakeLists.txt line 76
By syntheticpp:

It's only needed to fix linker errors when building the tests.
Clang does not seem to support gcc's __thread specifier, which seems to by used by gtest.
The -pthread flag cflags enables in libc some subs.