Remove warning when compiling to .bc file

emcc.py

@@ -541,8 +541,6 @@ def get_clang_command_asm():
     return compiler + compile.get_target_flags()
 
   if state.mode == Mode.COMPILE_ONLY:
-    if options.output_file and get_file_suffix(options.output_file) == '.bc' and not options.lto and '-emit-llvm' not in state.orig_args:
-      diagnostics.warning('emcc', '.bc output file suffix used without -flto or -emit-llvm.  Consider using .o extension since emcc will output an object file, not a bitcode file')
     if all(get_file_suffix(i) in ASSEMBLY_EXTENSIONS for i in options.input_files):
       cmd = get_clang_command_asm() + newargs
     else:

test/test_other.py

@@ -594,12 +594,16 @@ def test_emcc_2(self, compiler, suffix):
       self.run_process([compiler, target, '-o', target + '.js'])
       self.assertContained('Hello, world!', self.run_js(target + '.js'))
 
-  def test_bc_output_warning(self):
-    err = self.run_process([EMCC, '-c', test_file('hello_world.c'), '-o', 'out.bc'], stderr=PIPE).stderr
-    self.assertContained('emcc: warning: .bc output file suffix used without -flto or -emit-llvm', err)
+  def test_bc_output_suffix(self):
+    # Emscripten doe not use the output name when compiling to decide on the type
+    # of output.  For example, specifying an output filename that ends in `.bc` does
+    # *not* imply the output is actually bitcode.
+    self.run_process([EMCC, '-c', test_file('hello_world.c'), '-o', 'out.bc'])
+    self.assertTrue(building.is_wasm('out.bc'))
 
   def test_bc_as_archive(self):
     self.run_process([EMCC, '-c', test_file('hello_world.c'), '-flto', '-o', 'out.a'])
+    self.assertTrue(is_bitcode('out.a'))
     self.run_process([EMCC, 'out.a'])
 
   @parameterized({