Add tools/run_tests/run_lcov.sh
This is a tool for collecting coverage reports from our tests and
combining them with the open-source tool 'lcov'.
diff --git a/Makefile b/Makefile
index 35c2d84..ae78f82 100644
--- a/Makefile
+++ b/Makefile
@@ -49,6 +49,15 @@
LDFLAGS_msan = -fsanitize=memory
DEFINES_msan = NDEBUG
+VALID_CONFIG_gcov = 1
+CC_gcov = gcc
+CXX_gcov = g++
+LD_gcov = gcc
+LDXX_gcov = g++
+CPPFLAGS_gcov = -O0 -fprofile-arcs -ftest-coverage
+LDFLAGS_gcov = -fprofile-arcs -ftest-coverage
+DEFINES_gcov = NDEBUG
+
# General settings.
# You may want to change these depending on your system.