Simplify tests
Simplify tests

We don't need to create new builder objects, the config is a reference,
so when we update it, the builder will see the new values.

Test: run ninja_tests (via build_prebuilts.sh)
Change-Id: I8d3e4ff530014eb034ae774fbadcea3d5359181c

mydongistiny/ninja,mydongistiny/ninja,mydongistiny/ninja,mydongistiny/ninja