🐛fix: missing popd on build script for Linux & macOS at cpp/quickstart

Author: takuya-o

content/en/docs/languages/cpp/quickstart.md

@@ -191,6 +191,7 @@ the steps of the previous section.
       pushd cmake/build
       cmake -DCMAKE_PREFIX_PATH=$MY_INSTALL_DIR ../..
       make -j 4
+      popd
       ```
 
     - Windows