Deduplicate activated configs in the .emscripten file (#198)

While doing so, we:

* keep the latest activation (e.g., the user may have activated latest and then latest-upstream, then the upstream LLVM is what is desired).
* keep the order of keys fixed (so the relative order of lines in the .emscripten file is fixed)

This adds some assertions in the Dockerfile, to verify we have one LLVM_ROOT command, and it is the right one.

Fixes #194

Author: kripken

Dockerfile

@@ -20,6 +20,8 @@ RUN cd /root/ \
  && /root/emsdk/emsdk activate latest-upstream \
  && source /root/emsdk/emsdk_env.sh --build=Release \
  && emcc hello_world.cpp -s WASM_OBJECT_FILES=1 \
+ && python -c "import os ; assert open(os.path.expanduser('~/.emscripten')).read().count('LLVM_ROOT') == 1" \
+ && python -c "import os ; assert 'upstream' in open(os.path.expanduser('~/.emscripten')).read()" \
  && echo "test fastcomp (waterfall)" \
  && /root/emsdk/emsdk install latest-fastcomp \
  && /root/emsdk/emsdk activate latest-fastcomp \
@@ -28,4 +30,3 @@ RUN cd /root/ \
  && emcc hello_world.cpp -s WASM=0 \
  && echo "test binaryen source build" \
  && /root/emsdk/emsdk install --build=Release binaryen-master-64bit
-

emsdk

@@ -1051,13 +1051,26 @@ def generate_dot_emscripten(active_tools):
   if embedded:
     cfg += "emsdk_path=os.path.dirname(os.environ.get('EM_CONFIG')).replace('\\\\', '/')\n"
 
+  # Different tools may provide the same activated configs; the latest to be
+  # activated is the relevant one.
+  activated_keys_in_order = []
+  activated_key_values = {}
+
   for tool in active_tools:
     tool_cfg = tool.activated_config()
     if tool_cfg:
-      tool_cfg = tool_cfg.replace(';', '\n')
-      if 'SPIDERMONKEY_ENGINE=' in tool_cfg: has_spidermonkey = True
-      if 'NODE_JS=' in tool_cfg: has_node = True
-      cfg += tool_cfg + '\n'
+      for specific_cfg in tool_cfg.split(';'):
+        name, value = specific_cfg.split('=')
+        if name not in activated_key_values:
+          activated_keys_in_order.append(name)
+        activated_key_values[name] = value
+
+  for name in activated_keys_in_order:
+    if name == 'SPIDERMONKEY_ENGINE':
+      has_spidermonkey = True
+    if name == 'NODE_JS':
+      has_node = True
+    cfg += name + ' = ' + activated_key_values[name] + '\n'
 
   # These two vars must always be defined, even though they might not exist.
   if not has_spidermonkey: cfg += "SPIDERMONKEY_ENGINE = ''\n"