[Bug testsuite/124066] EFFECTIVE_TARGETS flags are not visible to check_compile tests

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124066

--- Comment #8 from Richard Sandiford <rsandifo at gcc dot gnu.org> ---
The patches above are just a first step.  They make the effective target part
of the cache index, but they stop short of using the associated flags in
compiler tests.