emscripten: node_modules fix, cache location fix (#419893)

pkgs/development/compilers/emscripten/default.nix

@@ -114,15 +114,22 @@ stdenv.mkDerivation rec {
     cp -r . $appdir
     chmod -R +w $appdir
 
-    mkdir -p $appdir/node_modules
+    mkdir -p $appdir/node_modules/.bin
     cp -r ${nodeModules}/* $appdir/node_modules
+    cp -r ${nodeModules}/* $appdir/node_modules/.bin
+
+    cp ${./locate_cache.sh} $appdir/locate_cache.sh
+    chmod +x $appdir/locate_cache.sh
+
+    export EM_CACHE=$out/share/emscripten/cache
 
     mkdir -p $out/bin
     for b in em++ em-config emar embuilder.py emcc emcmake emconfigure emmake emranlib emrun emscons emsize; do
       makeWrapper $appdir/$b $out/bin/$b \
         --set NODE_PATH ${nodeModules} \
         --set EM_EXCLUSIVE_CACHE_ACCESS 1 \
-        --set PYTHON ${python3}/bin/python
+        --set PYTHON ${python3}/bin/python \
+        --run "source $appdir/locate_cache.sh"
     done
 
     # precompile libc (etc.) in all variants:

pkgs/development/compilers/emscripten/locate_cache.sh

@@ -0,0 +1 @@
+export EM_CACHE=${EM_CACHE:-"/tmp/$(basename $(realpath $(dirname $(which emcc))/..))_cache"}