Support for --gdb for target run-test.

Add a --gdb option for target run-test that starts the test with
gdbserver. So that this is clear it forces the test to be run in dev
mode too.

Change-Id: I539e30d49b6e0beea38c6e9c60abb16e3f4062f7
diff --git a/test/run-test b/test/run-test
index 739b589..46d966c 100755
--- a/test/run-test
+++ b/test/run-test
@@ -168,7 +168,7 @@
         echo "  Runtime Options:"
         echo "    -O             Run oatexec rather than oatexecd (off by default)."
         echo "    --debug        Wait for a debugger to attach."
-        #echo "    --gdb          Run under gdb; incompatible with some tests."
+        echo "    --gdb          Run under gdb; incompatible with some tests."
         echo "    --build-only   Build test files only (off by default)."
         echo "    --interpreter  Enable interpreter only mode (off by default)."
         echo "    --no-verify    Turn off verification (on by default)."