tests/tcg: honour the available QEMU binaries when running check-tcg

tests/tcg: honour the available QEMU binaries when running check-tcg

Currently configure can identify all the targets that have
cross-compilers available from the supplied target-list. By default
this is the default_target_list which is all possible targets we can
build.

At the same time the target list passed to meson is filtered down
depending on various factors including not building 64 bit targets on
32 bit hosts. As a result make check-tcg will erroneously attempt to
run tests for which we haven't built a QEMU.

Solve this by filtering the final list of TCG_TEST_TARGETS based on
what actually was configured by meson. Rename the variable that
configure spits out to TCG_TESTS_WITH_COMPILERS for clarity and to
avoid larger churn in the Makefile.

Message-ID: <20251204194902.1340008-4-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>