.gitignore: ignore test executables

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

.gitignore

@@ -61,6 +61,9 @@ autom4te.cache/
 .deps/
 src/opkg-cl
 tests/libopkg_test
+tests/opkg_active_list_test
+tests/opkg_extract_test
+tests/opkg_hash_test
 
 # Man pages
 man/*.1