configure: Avoid use of 'local' as it is non-POSIX

configure: Avoid use of 'local' as it is non-POSIX

We use the non-POSIX 'local' keyword in just two places in configure;
rewrite to avoid it.

In do_compiler(), just drop the 'local' keyword.  The variable
'compiler' is only used elsewhere in the do_compiler_werror()
function, which already uses the variable as a normal non-local one.

In probe_target_compiler(), $try and $t are both local; make them
normal variables and use a more obviously distinct variable name
for $t.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220825150703.4074125-8-peter.maydell@linaro.org