doc,test: clarify --eval syntax for leading '-' scripts #4329

Job	Run time
Build slim tarball	2m 10s
x86_64-darwin: with shared libraries	33m 35s
x86_64-linux: with shared libraries	21m 45s
aarch64-linux: with shared libraries	18m 29s
aarch64-darwin: with shared libraries	20m 35s
	1h 36m 34s

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