Improve warning message when ignore fake shared libraries. NFC (emscripten-core#23594)

Also, add a test for this warning which was previously not tested.

Author: sbc100

test/test_other.py

@@ -12866,9 +12866,12 @@ def test_euidaccess(self):
     self.do_other_test('test_euidaccess.c')
 
   def test_shared_flag(self):
+    self.run_process([EMCC, '-shared', test_file('hello_world.c'), '-o', 'libother.so'])
+
     # Test that `-shared` flag causes object file generation but gives a warning
-    err = self.run_process([EMCC, '-shared', test_file('hello_world.c'), '-o', 'out.foo'], stderr=PIPE).stderr
+    err = self.run_process([EMCC, '-shared', test_file('hello_world.c'), '-o', 'out.foo', 'libother.so'], stderr=PIPE).stderr
     self.assertContained('linking a library with `-shared` will emit a static object', err)
+    self.assertContained('emcc: warning: ignoring dynamic library libother.so when generating an object file, this will need to be included explicitly in the final link', err)
     self.assertIsObjectFile('out.foo')
 
     # Test that using an executable output name overrides the `-shared` flag, but produces a warning.

tools/link.py

@@ -2894,7 +2894,7 @@ def filter_out_fake_dynamic_libs(options, inputs):
   def is_fake_dylib(input_file):
     if get_file_suffix(input_file) in DYLIB_EXTENSIONS and os.path.exists(input_file) and not building.is_wasm_dylib(input_file):
       if not options.ignore_dynamic_linking:
-        diagnostics.warning('emcc', 'ignoring dynamic library %s because not compiling to JS or HTML, remember to link it when compiling to JS or HTML at the end', os.path.basename(input_file))
+        diagnostics.warning('emcc', 'ignoring dynamic library %s when generating an object file, this will need to be included explicitly in the final link', os.path.basename(input_file))
       return True
     else:
       return False