pkg-config file is broken when CMAKE_INSTALL_{INCLUDE,LIB}DIR is absolute #236
Description
As per title: src/wildmidi.pc.in has
prefix=@CMAKE_INSTALL_PREFIX@
exec_prefix=${prefix}
libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
includedir=${exec_prefix}/@CMAKE_INSTALL_INCLUDEDIR@
and so can’t handle absolute paths in CMAKE_INSTALL_{INCLUDE,LIB}DIR. This leads to a broken .pc file on NixOS in particular.
Similar to open-source-parsers/jsoncpp#1199. See “Concatenating paths when building pkg-config files” for a discussion of the problem and a suggested fix (I don’t know CMake myself, sorry).