Fix sed in compile script for BSD version in Mac

sed in Mac requires extension for backup file.
Signed-off-by: Geoffrey Métais <geoffrey.metais@gmail.com>

.gitignore

@@ -65,5 +65,6 @@ libVLC/build/
 
 #medialibrary build
 libvlc.pc
+libvlc.pc.backup
 libvlcpp.pc
 lib/

compile-libvlc.sh

@@ -832,7 +832,7 @@ sed "s#@prefix@#${MEDIALIBRARY_MODULE_DIR}/medialibrary/libvlcpp#g" $SRC_DIR/pkg
     $SRC_DIR/pkgs/libvlcpp.pc;
 sed "s#@libdir@#$SRC_DIR/libvlc/jni/libs/$ANDROID_ABI#g" $SRC_DIR/pkgs/libvlc.pc.in > \
     $SRC_DIR/pkgs/libvlc.pc;
-sed -i "s#@includedirs@#-I${SRC_DIR}/vlc/include \
+sed -i".backup" "s#@includedirs@#-I${SRC_DIR}/vlc/include \
 -I${SRC_DIR}/vlc/build-android-$TARGET_TUPLE/include#g" $SRC_DIR/pkgs/libvlc.pc;
 
 if [ ! -d "build-android-$ANDROID_ABI/" ]; then