Don't warn about asm.js optimization issues with wasm2js (#9897)

(as wasm2js doesn't emit asm.js anyhow)

Author: kripken

emcc.py

@@ -1134,7 +1134,9 @@ def check(input_file):
       shared.Settings.USE_CLOSURE_COMPILER = options.use_closure_compiler
       if not shared.check_closure_compiler():
         exit_with_error('fatal: closure compiler is not configured correctly')
-      if options.use_closure_compiler == 2 and shared.Settings.ASM_JS == 1:
+      # when we emit asm.js, closure 2 would break that, so warn (note that
+      # with wasm2js in the wasm backend, we don't emit asm.js anyhow)
+      if options.use_closure_compiler == 2 and shared.Settings.ASM_JS == 1 and not shared.Settings.WASM_BACKEND:
         shared.WarningManager.warn('ALMOST_ASM', 'not all asm.js optimizations are possible with --closure 2, disabling those - your code will be run more slowly')
         shared.Settings.ASM_JS = 2