ci: apt-install libgtest-dev/libgmock-dev and add build_gtest.sh in Dockerfile

app/Dockerfile

@@ -78,9 +78,13 @@ RUN set -eux; \
       libqt6webkit6-dev || true; \
     # Try to install Grantlee / KDReports via apt (preferred); ignore failures
     apt-get install -y --no-install-recommends libgrantlee5 libgrantlee5-dev libkdreports-dev || true; \
+    # Install GoogleTest dev packages so CMake can find GTest; build if apt provides sources
+    apt-get install -y --no-install-recommends libgtest-dev libgmock-dev || true; \
     # Build Grantlee and KDReports via scripts in /app if apt packages not available
     /app/build_grantlee.sh || true; \
     /app/build_kdreports.sh || true; \
+    # If libgtest-dev provided sources, build+install them via script
+    /app/build_gtest.sh || true; \
     # geographiclib already installed via apt; RTI (Proprietary) cannot be installed automatically
     echo "Note: RTI Connext (RTI) is proprietary and must be installed manually into /opt/RTI if required."