Move strtod_l check to CMake since it's very system-specific

include/fmt/posix.h

@@ -261,12 +261,6 @@ class file {
 // Returns the memory page size.
 long getpagesize();
 
-#if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) &&                        \
-    !defined(__ANDROID__) && !defined(__CYGWIN__) && !defined(__OpenBSD__) && \
-    !defined(__NEWLIB_H__)
-#  define FMT_LOCALE
-#endif
-
 #ifdef FMT_LOCALE
 // A "C" numeric locale.
 class Locale {