Check if test was killed by signal in makeTestFile.

Tests killed by a signal should cause the .t script to exit with an
error code, otherwise its exit code will be 0, and the test harness
won't be aware of the unsuccessful exit.

This change also makes the test runner more robust, so attaching to a
running test (e.g. with gdb or strace) won't cause the .t script to
exit.

src/tools/makeTestfile.pl

@@ -140,6 +140,8 @@ else {
     ######################################## Code for Unix run-hosts
     print $OUT <<__UNIX__;
 
+use POSIX qw(WIFEXITED WIFSIGNALED WEXITSTATUS);
+
 my \$pid = fork();
 die "\$tool: Can't fork for '$error': \$!\\n"
     unless defined \$pid;
@@ -154,9 +156,19 @@ if (\$pid) {
     };
 
     alarm \$timeout;
-    waitpid \$pid, 0;
-    alarm 0;
-    exit \$? >> 8;
+    while (1) {
+        waitpid \$pid, 0;
+        if (WIFEXITED(\$?)) {
+            # normal exit
+            alarm 0;
+            exit WEXITSTATUS(\$?);
+        } elsif (WIFSIGNALED(\$?)) {
+            # terminated by signal
+            alarm 0;
+            die "\$tool: Test was terminated by signal '\$?'\\n";
+        }
+        # non-terminal change of status, continue waiting
+    }
 }
 else {
     # Child process