Add CI workflow for cross-compiling Crystal on MSYS2 #12596

Job	Run time
x86_64-gnu-test (1.7.3)	34m 8s
x86_64-gnu-test (1.8.2)	34m 49s
x86_64-gnu-test (1.9.2)	34m 24s
check_format	1m 35s
x86_64-gnu-test (1.10.1)	34m 39s
x86_64-gnu-test-preview_mt	5m 38s
x86_64-gnu-test (1.11.2)	35m 24s
x86_64-gnu-test (1.12.2)	35m 22s
x86_64-musl-test	38m 4s
x86_64-gnu-test (1.13.3)	33m 37s
x86_64-gnu-test (1.14.0)	35m 32s
x86_64-gnu-test (1.0.0, FLAGS=-Dwithout_ffi USE_PCRE1=true)	33m 2s
x86_64-gnu-test (1.1.1, FLAGS=-Dwithout_ffi USE_PCRE1=true)	34m 7s
x86_64-gnu-test (1.2.2, USE_PCRE1=true)	34m 23s
x86_64-gnu-test (1.3.2, USE_PCRE1=true)	34m 6s
x86_64-gnu-test (1.4.1, USE_PCRE1=true)	35m 26s
x86_64-gnu-test (1.5.1, USE_PCRE1=true)	36m 17s
x86_64-gnu-test (1.6.2, USE_PCRE1=true)	35m 32s
	9h 26m 5s

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