configure: Restrict TCG to emulation

If we don't need to emulate any target, we certainly don't need TCG.

This should also help to compile again with
 ".../configure --enable-tools --disable-system --disable-user"
on systems that do not have a TCG backend.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[thuth: Re-arranged the code, remove check-softfloat from buildtest.yml]
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220706153816.768143-1-thuth@redhat.com>
2 files changed