Fix warning maybe-uninitialized in install-dependencies

Recent versions of gcc changed some rule about uninitialized variables, causing a warning which is for some reason considered as an error when I try to run `bootstrap.sh`. See google/googletest#3219 and google/googletest#3024

This fixes it by applying a patch  which is already in the master branch of googletest, but not in the release version used by the script.

tools/install-dependencies

@@ -31,6 +31,8 @@ cp $ROOT/tools/*.patch .
 patch CMakeLists.txt gtest.patch
 patch googletest/CMakeLists.txt gtest_test.patch
 patch googlemock/CMakeLists.txt gtest_mock.patch
+# see https://github.com/google/googletest/pull/3024
+sed -i 's/int dummy;/int dummy = 0;/g' googletest/src/gtest-death-test.cc
 
 cmake -DCMAKE_INSTALL_PREFIX:PATH=$PREFIX -H.
 make -j4