In pch-bridging-header-deps test, the PathSanitizingFileCheck is used to
check against YAML escaped paths. This works for Unix paths, since the
slash doesn't need to be escaped, but doesn't work for Windows paths,
because the path separator is escaped, and the replacement done by
PathSanitizingFileCheck only looks for exact matches.
To avoid changes in how Darwin/Linux execute the tests, this commit adds
two options in PathSanitizingFileCheck: Windows compatibility makes the
given paths match both forward and backward slashes; in the additional
YAML compatibility is enabled, escaped backward slashes will also be
matched.
The Windows compatibility is enabled for all the test in case the tests
are running on Windows (change done in lit.cfg), while the YAML
compatibility is only enabled for those tests that might need it (like
the PCH bridging header one). This is in order to not allow possible
empty path components in tests that do not deal with YAML escaped paths.
'%FileCheck' removes absolute paths of the source and build directory
from the input. Overwhelming majority of tests don't intend to match
these paths.
Also add a substitution '%raw-FileCheck' that does not sanitize the
input.
