Differences in PKG_CONFIG_PATH between MinGW and Cygwin

When you're compiling some Linux library for Windows you can get the errors like these:

Package gthread-2.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gthread-2.0.pc' to the PKG_CONFIG_PATH environment variable
No package 'gthread-2.0' found

It's pretty straightforward for MinGW. Just do "export PKG_CONFIG_PATH = ~/lib/pkgconfig" where ~/lib/pkgconfig is the place your pkgconfig files are stored.

For Cygwin it does not work this way. It should be a real Windows path, not the Linux-style path. For example "export PKG_CONFIG_PATH=c:\\cygwin\\home\\mlt\\lib\\pkgconfig" will work.

It took a while to realize since ProcessMonitor does not show any attempts to find gthread-2.0.pc file. Who knows why?