prepend package search directories to $INCFLAGS and $LIBPATH
append compiler and linker flags to $CFLAGS and $libs
Note that we use $LIBPATH instead of $LDFLAGS so that shared libraries will be found again thanks to the -Wl,-rpath linker flag that is added by MakeMakefile
Note that we use $LIBPATH instead of $LDFLAGS so that shared libraries will be found again thanks to the
-Wl,-rpath
linker flag that is added by MakeMakefile