Reapply "Change test_module_config from copying files to symlink ..."

This reverts commit c6a321e4.

Original commit broke whe building sdk/ndk in postsubmit because of
missing target arch.

See: https://android-build.corp.google.com/artifact/submitted/11914755/mainline_modules_sdks-trunk_staging-userdebug/latest/view/logs%2Fbuild_error.log

Reapplying originaly commit and adding fix in patchest.

Test: DIST_DIR=/usr/local/google/dist/bug TARGET_RELEASE=trunk_staging TARGET_BUILD_VARIANT=userdebug UNBUNDLED_BUILD_SDKS_FROM_SOURCE=true packages/modules/common/build/mainline_modules_sdks.sh
Test: m general-tests
Change-Id: Id844feb7ff9750bcd5af890a9fd26f7342344965