ci: consolidate build and test steps in Dockerfile

- Merge the LPM build and test instructions on the same RUN layer to mitigate the cached vs compiled version missmatch related problem that causes build instability intermittently

build_system/ubuntu/Dockerfile.libpointmatcher.ci_PR

@@ -40,21 +40,21 @@ WORKDIR "${NBS_LIB_INSTALL_PATH}/${NBS_REPOSITORY_NAME}"
 RUN chmod +x ./utest/listVersionsUbuntu.sh
 RUN utest/listVersionsUbuntu.sh
 
-# ==== Build libpointmatcher checkout branch ======================================================
+# ==== Build/test libpointmatcher checkout branch =================================================
 WORKDIR ./build_system/ubuntu
 
 RUN chmod +x lpm_install_libpointmatcher_ubuntu.bash
 RUN chmod +x lpm_execute_libpointmatcher_unittest.bash
 RUN chmod +x entrypoint.bash
 
-
+# Note: keep build and test instructions on the same RUN layer to mitigate the cached vs compiled
+# version missmatch related problem that causes build instability
 RUN bash lpm_install_libpointmatcher_ubuntu.bash \
     --repository-version ${REPOSITORY_VERSION} \
     --cmake-build-type ${CMAKE_BUILD_TYPE} \
-    ${INSTALL_SCRIPT_FLAG}
-
-# ==== Execute libpointmatcher unit-test===========================================================
-RUN source lpm_execute_libpointmatcher_unittest.bash
+    ${INSTALL_SCRIPT_FLAG} \
+    && echo "Execute libpointmatcher unit-test" \
+    && bash lpm_execute_libpointmatcher_unittest.bash
 
 # .................................................................................................
 ## Alternate version