Build issue when libmp3splt is installed in custom directory

[TurtleWilly]

./common.h:41:10: fatal error: 'libmp3splt/mp3splt.h' file not found
#include <libmp3splt/mp3splt.h>
         ^
1 error generated.

$ PKG_CONFIG_PATH=/usr/local/silo/mp3splt/2.6.2/lib/pkgconfig pkg-config --cflags libmp3splt
-I/usr/local/silo/mp3splt/2.6.2/include/libmp3splt

The pkg-config .pc file for libmp3splt specifically sets the include path to <prefix>/include/libmp3splt and not <prefix>/include only. So common.h should only include <mp3splt.h> for this to work. Alternatively the .pc file of the library only should set the include path to <prefix>/include.

Note: This issue only will trigger, if the installation prefix is very custom. If one installs to a standard location like /usr/local it won't trigger since /usr/local/include is in the compilers default include path anyway, so <libmp3splt/mp3splt.h> would resolve too (but not because of the specifications in the .pc file, but because of the compiler's default include paths).

I currently workaround it by passing: LIBMP3SPLT_CFLAGS='-I/my/custom/libmp3split/prefix/include' to mp3split's build.