meson: small cleanup for printf checks

Instead of duplicating checks add a use_system_printf meson variable and
macro and use them everywhere.

glib/gprintf.c

@@ -319,7 +319,7 @@ g_vasprintf (gchar      **string,
   gint len;
   g_return_val_if_fail (string != NULL, -1);
 
-#if !defined(HAVE_GOOD_PRINTF)
+#if !defined(USE_SYSTEM_PRINTF)
 
   len = _g_gnulib_vasprintf (string, format, args);
   if (len < 0)

glib/gprintfint.h

@@ -25,7 +25,7 @@
 #ifndef __G_PRINTFINT_H__
 #define __G_PRINTFINT_H__
 
-#ifdef HAVE_GOOD_PRINTF
+#ifdef USE_SYSTEM_PRINTF
 
 #define _g_printf    printf
 #define _g_fprintf   fprintf

glib/meson.build

@@ -12,7 +12,7 @@ endif
 # <https://github.com/mesonbuild/meson/issues/3937>. When we can depend
 # on a meson version where those are fixed, revert the commit that
 # introduced this workaround.
-if have_good_vsnprintf and have_good_snprintf and have_good_printf
+if use_system_printf
   gnulib_lib = []
   gnulib_objects = []
   gnulib_libm_dependency = []

meson.build

@@ -913,17 +913,16 @@ else
   glib_conf.set('EXEEXT', '')
 endif
 
-if have_good_vsnprintf and have_good_snprintf and have_good_printf
-  # Our printf is 'good' only if vsnpintf()/snprintf()/printf() supports C99 well enough
-  glib_conf.set('HAVE_GOOD_PRINTF', 1)
-else
+# Our printf is 'good' only if vsnpintf()/snprintf()/printf() supports C99 well enough
+use_system_printf = have_good_vsnprintf and have_good_snprintf and have_good_printf
+glib_conf.set('USE_SYSTEM_PRINTF', use_system_printf)
+glibconfig_conf.set('GLIB_USING_SYSTEM_PRINTF', use_system_printf)
+
+if not use_system_printf
+  # gnulib has vasprintf so override the previous check
   glib_conf.set('HAVE_VASPRINTF', 1)
 endif
 
-glibconfig_conf.set('GLIB_USING_SYSTEM_PRINTF',
-                    have_good_vsnprintf and have_good_snprintf and have_good_printf)
-
-
 # Check for nl_langinfo and CODESET
 if cc.links('''#include <langinfo.h>
                int main (int argc, char ** argv) {