fix failure of configure to detect gcc due to message translations

based on patch by Vadim Ushakov. in general overriding LC_ALL rather
than specific categories (here, LC_MESSAGES) is undesirable, but
LC_ALL is easier and in this case there is nothing else that depends
on the locale in this invocation of the compiler.

configure

@@ -204,7 +204,7 @@ fi
 # musl-gcc wrapper, and for critical bug detection in some gcc versions.
 #
 printf "checking whether compiler is gcc... "
-if fnmatch '*gcc\ version*' "$($CC -v 2>&1)" ; then
+if fnmatch '*gcc\ version*' "$(LC_ALL=C $CC -v 2>&1)" ; then
 cc_is_gcc=yes
 else
 cc_is_gcc=no