Allow skipping compiler tool specs that require Git #3457

Job	Run time
check_format	1m 37s
x86_64-gnu-test (1.7.3)	35m 0s
x86_64-gnu-test-preview_mt	5m 31s
x86_64-gnu-test (1.8.2)	34m 30s
x86_64-musl-test	36m 58s
x86_64-gnu-test (1.9.2)	34m 24s
x86_64-gnu-test (1.10.1)	35m 38s
x86_64-gnu-test (1.11.2)	34m 1s
x86_64-gnu-test (1.12.2)	35m 32s
x86_64-gnu-test (1.13.3)	34m 43s
x86_64-gnu-test (1.14.0)	34m 47s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	32m 40s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	35m 43s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	35m 11s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	33m 12s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	34m 50s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	34m 22s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	37m 0s
	9h 25m 39s

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