pkg-config: Use CMake install paths for lib, include (#1133)

Author: ckastner

ggml.pc.in

@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-includedir=${prefix}/include
-libdir=${prefix}/lib
+includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
 
 Name: ggml
 Description: The GGML Tensor Library for Machine Learning