Making it clearer that buildSrc/tests moved to buildSrc-tests

Bug: 138456696
Change-Id: I669237f339cd1278ceb03481643665388b4f3e87

diff --git a/buildSrc/README.md b/buildSrc/README.md
new file mode 100644
index 0000000..a3c72f7
--- /dev/null
+++ b/buildSrc/README.md

@@ -0,0 +1,6 @@
+This is the buildSrc project.
+Gradle builds (and tests) this project before the other projects, and Gradle adds its artifacts into the classpath of the other projects when configuring them.
+
+Tests for the buildSrc project are located in the buildSrc-tests project, so that the build doesn't need to wait for those tests to complete
+
+To run these tests you can run `./gradlew :buildSrc-tests:test`