ci: use mvn verify phase instead of install

Installing the artifacts is not necessary, and
currently we have to remove them from the build
cache to prevent that from growing too large

ci/build.sh

@@ -15,4 +15,4 @@ if [ ! -f "${GLSLANG_ARCHIVE}" ] || [ ! -d "${GLSLANG_DIR}" ] || ! echo "${GLSLA
   unzip -o -q "${GLSLANG_ARCHIVE}" -d "${GLSLANG_DIR}"
 fi
 
-mvn clean install --settings ci/settings.xml -Dglslang.path="${GLSLANG_DIR}/bin/glslangValidator"
+mvn verify --settings ci/settings.xml -Dglslang.path="${GLSLANG_DIR}/bin/glslangValidator"