configure: Do not force pie=no for non-x86

configure: Do not force pie=no for non-x86

PIE is supported on many other hosts besides x86.

The default for non-x86 is now the same as x86: pie is used
if supported, and may be forced via --enable/--disable-pie.

The original commit (40d6444e91c) said:

  "Non-x86 are not changed, as they require TCG changes"

but I think that's wrong -- there's nothing about PIE that
affects TCG one way or another.

Tested on aarch64 (bionic) and ppc64le (centos 7) hosts.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>