Use -fdebug-default-version=4 for assembly files

-fdebug-default-version=5 is causing $TMPDIR to end up in the dwarf
debug data, which causes the buildbot results to be nondeterministic.
Pass -fdebug-default-version=4 for assembly files as a workaround.

Bug: 235105792
Test: lunch aosp_arm-userdebug && m libbase && llvm-dwarfdump --debug-line out/target/product/generic/symbols/system/lib/libbase.so
Change-Id: Ife04e3c898bbb1291f71b8365fbca854cd2d2b66