Do not call the undeclared exit function.  Implicit function
declarations are likely not going to be supported by future compilers
by default, changing the outcome of this configure probe.

Submitted upstream: <https://gitlab.gnome.org/GNOME/gimp/-/merge_requests/810>

diff --git a/configure b/configure
index 6e62da8e3c164f82..f1c447baf7ff68f7 100755
--- a/configure
+++ b/configure
@@ -28898,17 +28898,17 @@ else $as_nop
 	  char *shmaddr;
 	id = shmget (IPC_PRIVATE, 4, IPC_CREAT | 0600);
 	if (id == -1)
-	  exit (2);
+	  return 2;
 	  shmaddr = shmat (id, 0, 0);
 	  shmctl (id, IPC_RMID, 0);
 	  if ((char*) shmat (id, 0, 0) == (char*) -1)
 	  {
 	    shmdt (shmaddr);
-	    exit (1);
+	    return 1;
 	  }
 	  shmdt (shmaddr);
 	  shmdt (shmaddr);
-	  exit (0);
+	  return 0;
 	}
 
 _ACEOF
diff --git a/configure.ac b/configure.ac
index d73f56228712f59d..32d2a072863ae64f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1284,17 +1284,17 @@ elif test "x$shmtype" = "xsysv"; then
 	  char *shmaddr;
 	id = shmget (IPC_PRIVATE, 4, IPC_CREAT | 0600);
 	if (id == -1)
-	  exit (2);
+	  return 2;
 	  shmaddr = shmat (id, 0, 0);
 	  shmctl (id, IPC_RMID, 0);
 	  if ((char*) shmat (id, 0, 0) == (char*) -1)
 	  {
 	    shmdt (shmaddr);
-	    exit (1);
+	    return 1;
 	  }
 	  shmdt (shmaddr);
 	  shmdt (shmaddr);
-	  exit (0);
+	  return 0;
 	}
       ]])],
       [AC_DEFINE([IPC_RMID_DEFERRED_RELEASE],[1],