[Docs] Update faq.md (#28)

Author: haochengxia

docs/src/en/faq.md

@@ -2,4 +2,19 @@
 
 1.  How to resolve when pip install fails?
 
-See [installation](https://cachemon.github.io/libCacheSim-python/getting_started/installation/).
+    See [installation](https://cachemon.github.io/libCacheSim-python/getting_started/installation/).
+
+2.  Get an error message like "cannot find Python package" when building.
+
+    The reason is that when building a Python binding package, we need the header and other necessary modules.
+    
+    If you can install software directly,
+
+    ```shell
+    [sudo] apt install python3-dev
+    ```
+    If not, please install Python somewhere and set environment variables to help the building system find them.
+    
+    ```shell
+    export CMAKE_ARGS="-DPython3_ROOT_DIR=${Python3_ROOT_DIR} -DPython3_INCLUDE_DIR=${Python3_INCLUDE_DIR} -DPython3_EXECUTABLE=${Python3_EXECUTABLE}"
+    ```