Reapply the change after fixing sanitizer errors.
The original problem was that `StringRef`s in `Matches` are pointing to
temporary local `std::string`s created by `path::convert_to_slash` in
the regex match call. This patch does the conversion up front in
container `FilePath`.
This reverts commit 2966f0fa505266735dbc8324b8821b7f0aa901ff.
Differential Revision: https://reviews.llvm.org/D124964
This patch transforms the given input headers to relative include names
using header search entries and some heuritics.
For example: `/Path/To/Header.h` will be included as `<Header.h>` with a
search path of `-I /Path/To/`; and
`/Path/To/Framework.framework/Headers/Header.h` will be included as
`<Framework/Header.h>`, given a search path of `-F /Path/To`.
Headermaps will also be queried in reverse to find a spelled name to
include headers.
Differential Revision: https://reviews.llvm.org/D123831
