The GCC check-tcg (user) test in particular was very prone to timing
out on Travis. We only actually need to move the some-softmmu builds
across as we already have coverage for linux-user.

As --enable-debug-tcg does increase the run time somewhat as more
debug is put in let's restrict that to just the plugins build. It's
unlikely that a plugins enabled build is going to hide a sanity
failure in core TCG code so let the plugin builds do the heavy lifting
on checking TCG sanity so the non-plugin builds can run swiftly.

Now the only remaining check-tcg builds on Travis are for the various
non-x86 arches.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20201117173635.29101-5-alex.bennee@linaro.org>