configure: Fix error message when C compiler is not working

configure: Fix error message when C compiler is not working

If you try to run the configure script on a system without a working
C compiler, you get a very misleading error message:

 ERROR: Unrecognized host OS (uname -s reports 'Linux')

Some people already opened bug tickets because of this problem:

 https://gitlab.com/qemu-project/qemu/-/issues/2057
 https://gitlab.com/qemu-project/qemu/-/issues/2288

We should rather tell the user that we were not able to use the C
compiler instead, otherwise they will have a hard time to figure
out what was going wrong.

While we're at it, let's also suppress the "unrecognized host CPU"
message in this case since it is rather misleading than helpful.

Fixes: 264b803721 ("configure: remove compiler sanity check")
Message-ID: <20240513114010.51608-1-thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>