malloc.c: silence "unused result" compiler warning

Before:

    malloc.c: In function ‘getpages’:
    malloc.c:273:34: warning: ignoring return value of ‘write’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
      273 | #    define fatalcroak(mess)    (write(2, (mess), strlen(mess)), exit(2))
          |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    malloc.c:1546:21: note: in expansion of macro ‘fatalcroak’
     1546 |                     fatalcroak("panic: Off-page sbrk\n");
          |                     ^~~~~~~~~~
    malloc.c:273:34: warning: ignoring return value of ‘write’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
      273 | #    define fatalcroak(mess)    (write(2, (mess), strlen(mess)), exit(2))
          |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    malloc.c:1585:13: note: in expansion of macro ‘fatalcroak’
     1585 |             fatalcroak("Misalignment of sbrk()\n");
          |             ^~~~~~~~~~
    gcc -c -DPERL_CORE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -std=c99 -O2 -Wall -Werror=pointer-arith -Werror=vla -Wextra -Wno-long-long -Wno-declaration-after-statement -Wc++-compat -Wwrite-strings -Wno-use-after-free universal.c

(The "make depend" comment was overlooked in commit b9e5552.)

Author: mauke

malloc.c

@@ -269,9 +269,9 @@
 #  define MALLOC_UNLOCK		MUTEX_UNLOCK(&PL_malloc_mutex)
 #endif 
 
-#  ifndef fatalcroak				/* make depend */
-#    define fatalcroak(mess)	(write(2, (mess), strlen(mess)), exit(2))
-#  endif 
+#ifndef fatalcroak
+#  define fatalcroak(mess)      STMT_START { PERL_UNUSED_RESULT(write(2, (mess), strlen(mess))); exit(2); } STMT_END
+#endif
 
 #ifdef DEBUGGING
 #  undef DEBUG_m