build-unit-test-docker: gcov has to be the same version as gcc

Change-Id: I0461f78da12ce94e38a53ca6954f4c3845c0d121
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index bd02a1d..6d35866 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -210,7 +210,11 @@
     protobuf-compiler
 
 # Make gcc8 and g++8 the default
-RUN update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 800 --slave /usr/bin/g++ g++ /usr/bin/g++-8
+RUN update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 800 \
+  --slave /usr/bin/g++ g++ /usr/bin/g++-8 \
+  --slave /usr/bin/gcov gcov /usr/bin/gcov-8 \
+  --slave /usr/bin/gcov-dump gcov-dump /usr/bin/gcov-dump-8 \
+  --slave /usr/bin/gcov-tool gcov-tool /usr/bin/gcov-tool-8
 
 RUN pip install inflection
 RUN pip install pycodestyle