Makefile.am: Don't include objectiveC sources in libmedialibrary.la
Makefile.am: Don't include objectiveC sources in libmedialibrary.la

This makes LIBTOOL assume an objc linker will have to be used, even
when sources are conditionaly appended.
Using such a linker makes cross compilation to android fail.

chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary