Add googletest wrap file

With this, unit tests can be run in a standalone session.

Tested:
Standalone tests work:

```
1/4 test_systemd_parser                   OK              0.01s
2/4 test_systemd_signal                   OK              0.01s
3/4 test_hypervisor_state                 OK              0.01s
4/4 test_scheduled_host_transition        OK              0.01s

Ok:                 4
Expected Fail:      0
Fail:               0
Unexpected Pass:    0
Skipped:            0
Timeout:            0
```

Change-Id: I434320257498a891af5f15835fdee9927e7d5aee
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/subprojects/googletest.wrap b/subprojects/googletest.wrap
new file mode 100644
index 0000000..56da9ef
--- /dev/null
+++ b/subprojects/googletest.wrap
@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://github.com/google/googletest
+revision = HEAD