Microoptimize package name extraction.

Since there's only one, and it appears early, we can stop when we find
it rather than trawl through megabytes of localized strings we don't
need to see.

Bug: https://github.com/onetrueawk/awk/issues/199#issuecomment-1756885708
Test: treehugger
Change-Id: If4d7c63da7df76c23fca417a4b727189f79e3ce6