add LOCAL_DISABLE_TEST_CONFIG logic

Disable the generation of .config file when the variable
LOCAL_DISABLE_TEST_CONFIG is true.

Bug: 188927912
Test: rum 'm module-name' (`android_test_helper_app` type module)
Test: TreeHugger
Change-Id: I64372b4ba84fcf1af937abdee345ceb1d3c2f6c5