realpath fails on MacOS 11.1 (big sur), with bugfix

realpath() is failing to compile for me on MacOS 11.1 on an Apple M1 Mac.  I encountered this when building GNU Global Tags from the most recent source archive at global-6.6.5.tar.gz <http://tamacom.com/global/global-6.6.5.tar.gz>.  

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.

The Brew folks and the Global Tags folks told me to report the bug here.