Add missing gtest install script

Author: TheAssassin

ci/install-gtest.sh

@@ -0,0 +1,22 @@
+#! /bin/bash
+
+set -euxo pipefail
+
+tempdir="$(mktemp -d)"
+
+_cleanup() {
+    [[ -d "$tempdir" ]] && rm -r "$tempdir"
+}
+trap _cleanup EXIT
+
+cd "$tempdir"
+
+#git clone https://github.com/google/googletest -b release-1.8.1 .
+git clone https://github.com/google/googletest -b v1.13.0 .
+
+mkdir build
+cd build
+
+cmake .. -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr
+make -j6
+make install