Path constraints differ between different file systems. For instance, the Windows file system does not care about path casing. Clang also tries to leverage that fact by changing the casing of some of the system header paths, which makes it harder to provide working values for --include/exclude-headers.

We can make the header path matching more lenient by relying on the file system specific path matching logic provided through FileSystem::getPathMatcher (https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/FileSystem.html#getPathMatcher(java.lang.String))

This will do the right thing appropriate to the file system. For instance; making matching case insensitive on Windows.

See also discussion: https://mail.openjdk.java.net/pipermail/panama-dev/2019-March/004975.html