build: enable code coverage

Enable code coverage for the project.  Valgrind not enabled in this
step.

Change-Id: I62891f6054e5e5315d7f150a1f3dcf619f2740db
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/.lcovrc b/.lcovrc
new file mode 100644
index 0000000..360a8b4
--- /dev/null
+++ b/.lcovrc
@@ -0,0 +1,3 @@
+geninfo_gcov_all_blocks = 1
+lcov_function_coverage = 1
+lcov_branch_coverage = 0