efl: refactor CFLAGS, LIBS, LIBADD and LDADD usage.
- remove EFL_LIBS and EFL_CFLAGS, use per-lib values that inherit from EFL (general)
- add NAME_LDFLAGS and EFL_LDFLAGS for linker flags.
- LDADD (binaries) now use NAME_LDFLAGS instead of NAME_LIBS, as they link to libname.la and that will pull in the libtool dependencies