Clear PYTHONHOME when using bundled python (#600)

Fixes: #598

emsdk

@@ -6,13 +6,31 @@
 
 # Wrapper script that runs emsdk.py
 
+# First look for pre-built python (macos)
 if [ -z "$EMSDK_PYTHON" ]; then
-  # Look for python3 first.  This is especially important on macOS (See:
-  # https://github.com/emscripten-core/emsdk/pull/273)
-  EMSDK_PYTHON=$(which python3 2> /dev/null)
-  if [ $? != 0 ]; then
-    EMSDK_PYTHON=python
+  PYTHON3=$(dirname $0)/python/3.7.4-2_64bit/bin/python3
+  if [ -e $PYTHON3 ]; then
+    EMSDK_PYTHON=$PYTHON3
+    # When using our bundled python we never want the users
+    # PYTHONHOME or PYTHONPATH
+    # https://github.com/emscripten-core/emsdk/issues/598
+    unset PYTHONHOME
+    unset PYTHONPATH
   fi
 fi
 
+# Look for `python3` first.  This is especially important on macOS (See:
+# https://github.com/emscripten-core/emsdk/pull/273)
+if [ -z "$EMSDK_PYTHON" ]; then
+  PYTHON3=$(which python3 2> /dev/null)
+  if [ $? = 0 ]; then
+    EMSDK_PYTHON=$PYTHON3
+  fi
+fi
+
+# Finally fall back to just looking for `python` in PATH
+if [ -z "$EMSDK_PYTHON" ]; then
+  EMSDK_PYTHON=python
+fi
+
 exec "$EMSDK_PYTHON" "$0.py" "$@"