test: Allow optional usage of vendored googletest

Change-Id: I2646b01eefa954b1afc70ecc04791d53b99d96d7
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/subprojects/googletest.wrap b/subprojects/googletest.wrap
new file mode 100644
index 0000000..fb55947
--- /dev/null
+++ b/subprojects/googletest.wrap
@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://github.com/google/googletest
+revision = release-1.10.0