The current approach was to parse the .pc and, detect the prefix, throw
everything together and at the end replace all \ with / to not produce invalid
escape sequences.
This has the problem that escaping in .pc files is ignored and no longer
possible. Also in case the prefix path has a space in it the result would be
invalid because of missing escaping.
This changes the following things:
* We no longer normalize values at the end. Instead we assume .pc files use "/"
as a directory separator or "\\", same format as under Unix. "\" alone no
longer works. This shouldn't be a problem since most build tools produce .pc
files with "/" like meson, cmake, autotools.
* When injecting the prefix at runtime we convert the prefix to use "/" and
escape spaces so that in combination with the .pc content the result is a
valid escaped path value again.
This patch has been used in MSYS2 for some months now.
See #212
Christoph Reiter