Warn on emterpreter usage

Seems like a good first step before #11020.

Author: sbc100

ChangeLog.md

@@ -17,6 +17,7 @@ See docs/process.md for how version tagging works.
 
 Current Trunk
 -------------
+- Add warning on use of `EMTERPRETIFY` which is due to be removed.
 - Emscripten can now compile assembly files in llvm's .s/.S file format.
 - Remove test-only environment variable handling for `EMCC_LEAVE_INPUTS_RAW`.
   The two uses cases in our test code were covered by the `-nostdlib` option.

emcc.py

@@ -1415,6 +1415,7 @@ def has_c_source(args):
         exit_with_error('ASYNCIFY has been removed from fastcomp. There is a new implementation which can be used in the upstream wasm backend.')
 
     if shared.Settings.EMTERPRETIFY:
+      diagnostics.warning('emterpreter', 'emterpreter is soon to be deprecated.  If you depend on this feature please reach out on github for help transiationing.')
       shared.Settings.FINALIZE_ASM_JS = 0
       shared.Settings.SIMPLIFY_IFS = 0 # this is just harmful for emterpreting
       shared.Settings.EXPORTED_FUNCTIONS += ['emterpret']

tools/shared.py

@@ -66,6 +66,7 @@
 diagnostics.add_warning('emcc')
 diagnostics.add_warning('undefined')
 diagnostics.add_warning('version-check')
+diagnostics.add_warning('emterpreter')
 diagnostics.add_warning('unused-command-line-argument', shared=True)