build-gnu.sh: Remove || true

[oech3]

We should catch error instead of ignoring.

[oech3]

Very simple PR. But cc @naoNao89 for the sake.

[codspeed-hq]

CodSpeed Performance Report

Merging #9256 will not alter performance

_{Comparing oech3:gtest-catch-err (e1548c4) with main (d432131)}

Summary

✅ 123 untouched
⏩ 5 skipped¹

Footnotes

1. 5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)