make warnings for sac2c on ubuntu 21.10
Version 41ed2a07 of sac2c gets this warning during make:
/home/sac/sac2c/src/libsac2c/support/system.c: In function ‘SYSexec_and_read_output’:
[ 85%] Building C object src/libsac2c/CMakeFiles/sac2cShared.dir/typecheck/create_wrapper_code.c.o
/home/sac/sac2c/src/libsac2c/support/system.c:282:5: warning: ‘fclose’ called on pointer returned from a mismatched allocation function [-Wmismatched-dealloc]
282 | fclose (f);
| ^~~~~~~~~~
/home/sac/sac2c/src/libsac2c/support/system.c:264:15: note: returned from ‘popen’
264 | FILE *f = popen (cmd, "r");
| ^~~~~~~~~~~~~~~~