indexer: Fix the build with trunk clang and with assertions enabled.
indexer: Fix the build with trunk clang and with assertions enabled.

CLANG_VERSION_FULL is a macro that lives in mozilla-central, so it doesn't exist
while building the indexer. Just use the macro clang provides.

bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox,bill-mccloskey/searchfox