Since commit efc6c070 ("configure: Add a test for the
minimum compiler version") the minimum compiler version
required for GCC is 4.8.

We can safely remove the special case for GCC 4.6 introduced
in commit 0448f5f8 ("cpu-exec: Fix compiler warning
(-Werror=clobbered)").
No change for Clang as we don't know.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20201210134752.780923-3-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>