run-gnu-tests-smack-ci.sh: Use multi-call binary for faster build

[oech3]

47.2 s -> 38.38 s at cargo

[oech3]

@ChrisDryden This script was duplicating the cping binaries.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing oech3:patch-6 (6d3df54) with main (8f2c3c5)}

Summary

✅ 142 untouched benchmarks
⏩ 37 skipped benchmarks¹

Footnotes

1. 37 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:

Congrats! The gnu test tests/tail/pid-pipe is no longer failing!

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/env/env-signal-handler is now passing!