feat: (revert) upgrade emsdk to 4.0.13

This reverts commit 25c91d5.
There are still problems with libxml2 and new LLVM also GDAL has problems with it.

Author: codeart1st

.github/actions/prepare-build-env/action.yml

@@ -9,8 +9,8 @@ runs:
       run: |
         git clone https://github.com/emscripten-core/emsdk.git
         cd emsdk
-        ./emsdk install 4.0.13
-        ./emsdk activate 4.0.13
+        ./emsdk install 3.1.68
+        ./emsdk activate 3.1.68
         source ./emsdk_env.sh
         # Export emsdk environment variables
         echo "PATH=$PATH" >> $GITHUB_ENV

README.md

@@ -107,7 +107,7 @@ git pull --recurse-submodules
 
 Start the build container with the following command to ensure the filesystem permissions for newly created files are correct.
 ```sh
-docker run -it --rm -v $(pwd):/src -v /etc/passwd:/etc/passwd --user "$(id -u):$(id -g)" --name mapserver-wasm emscripten/emsdk:4.0.13 bash
+docker run -it --rm -v $(pwd):/src -v /etc/passwd:/etc/passwd --user "$(id -u):$(id -g)" --name mapserver-wasm emscripten/emsdk:3.1.68 bash
 ```
 And execute in a second terminal the following command to install the missing build depedencies as root user.
 ```sh