Alpine is running with Musl libc and musl uses extended precision
doubles, while valgrind can't handle extended precision,
2.3 == atof("2.3") won't be true under valgrind.
And therefore the option retrieval methods *_get_double would fail.
Also we have to increase the test verbosity, as `SKIPm` doesn't print
the message when skipping the tests.
See: silentbicycle/greatest#85
ec3e47abb5