Package global fails to compile on MacOS 11.1

Package global failed to compile on my arm 11.1 system. This is due to an error because realpath cannot be found. The fix is to modify configure to include stdlib.h.

Line 14291 of configure on global-6.6.5:

main(){ (void)realpath("/./tmp", (void *)0); return 0; }
Insert one line before that:

#include<stdlib.h>
main(){ (void)realpath("/./tmp", (void *)0); return 0; }
configure now succeeds.