[ci] Revert emscripten to 4.0.21

Latest version reaches an internal compiler error.

Author: serge-sans-paille

.github/workflows/emscripten.yml

@@ -24,4 +24,4 @@ jobs:
         run: |
             echo "Build script for wasm"
             playwright install
-            ./test/test_wasm/test_wasm.sh
+            ./test/test_wasm/test_wasm.sh 4.0.21

test/test_wasm/test_wasm.sh

@@ -8,14 +8,14 @@ SRC_DIR=$TEST_WASM_DIR/../..
 
 # the emsdk dir can be passed as optional argument
 # if not passed, it will be downloaded in the current dir
-if [ $# -eq 0 ]
+if [ $# -eq 0 -o ! -d "$1" ]
 then
+    EMSCRIPTEN_VERSION=${1:-latest}
     git clone https://github.com/emscripten-core/emsdk
     cd emsdk
-    ./emsdk install latest
-    ./emsdk activate latest
+    ./emsdk install ${EMSCRIPTEN_VERSION}
+    ./emsdk activate ${EMSCRIPTEN_VERSION}
     source ./emsdk_env.sh
-
 else
     EMSCRIPTEN_DIR=$1
     source $EMSCRIPTEN_DIR/emsdk_env.sh
@@ -40,4 +40,4 @@ emmake make -j4
 cd ..
 
 # run tests in browser
-python $TEST_WASM_DIR/test_wasm_playwright.py  build/test
+python $TEST_WASM_DIR/test_wasm_playwright.py  build/test