Honor -g0 when it follows -g. (#16728)

Fixes: #16724

Author: sbc100

emcc.py

@@ -3072,10 +3072,10 @@ def consume_arg_file():
         # if we don't need to preserve LLVM debug info, do not keep this flag
         # for clang
         if settings.DEBUG_LEVEL < 3:
-          newargs[i] = ''
+          newargs[i] = '-g0'
         else:
-          # for 3+, report -g to clang as -g4 etc. are not accepted
-          newargs[i] = '-g'
+          # for 3+, report -g3 to clang as -g4 etc. are not accepted
+          newargs[i] = '-g3'
           if settings.DEBUG_LEVEL == 4:
             settings.GENERATE_SOURCE_MAP = 1
             diagnostics.warning('deprecated', 'please replace -g4 with -gsource-map')

tests/test_other.py

@@ -11904,3 +11904,10 @@ def test_in_tree_header_usage(self):
     create_file('test.c', '#include <emscripten.h>')
     err = self.expect_fail([EMCC, '-I' + path_from_root('system/include'), 'test.c'])
     self.assertContained('#error "Including files directly from the emscripten source tree is not supported', err)
+
+  def test_multiple_g_flags(self):
+    # Verify that a second -g argument overrides the first
+    self.run_process([EMCC, test_file('hello_world.c'), '-c', '-g'])
+    self.assertIn(b'.debug', read_binary('hello_world.o'))
+    self.run_process([EMCC, test_file('hello_world.c'), '-c', '-g', '-g0'])
+    self.assertNotIn(b'.debug', read_binary('hello_world.o'))