Update .gitignore for libretro builds.

.gitignore

@@ -62,7 +62,6 @@ build*/
 # Temp file used by jenkins windows build (TODO: remove)
 desc.txt
 
-
 Logs
 Memstick
 memstick
@@ -96,5 +95,8 @@ debian/files
 debian/ppsspp.substvars
 debian/ppsspp/
 
+# Libretro build
+*.o
+
 # YouCompleteMe file
 .ycm_extra_conf.pyc