Add #define __STDC_FORMAT_MACROS

This define is needed in order for the SCNx32/SCNu32 in find_tag() to be
compiled correctly on older `glibc`s.

desktop_version/src/editor.cpp

@@ -20,6 +20,9 @@
 #include <utf8/unchecked.h>
 #include <physfs.h>
 
+#ifndef __STDC_FORMAT_MACROS
+#define __STDC_FORMAT_MACROS
+#endif
 #include <inttypes.h>
 #include <cstdio>