Allow setting of CLOSURE_ARGS in ports

[ypujante]

This is the implementation that was discussed in #24109

I can update the Changelog in a later commit if the tests pass in CI and this PR is approved.

• I manually/locally ran other.test_closure_externs to make sure that the changes were not affecting existing code
• I added a test other.test_closure_args_from_port that piggy back on test_closure_externs to pass the same parameter in the port instead and make sure that these changes actually do what they are supposed to do in the first place.

Hopefully I didn't forget anything. The changes are pretty straightforward in the grand scheme of things.

[ypujante]

This is the only test that fails. It doesn't seem to be related to my changes but please let me know if it is.

======================================================================
FAIL [2.055s]: test_sdl_mouse (test_browser.browser_2gb)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/project/test/common.py", line 2353, in run_browser
    self.assertContained(expected, output)
  File "/root/project/test/common.py", line 1652, in assertContained
    self.fail("Expected to find '%s' in '%s', diff:\n\n%s\n%s" % (
  File "/usr/lib/python3.8/unittest/case.py", line 753, in fail
    raise self.failureException(msg)
AssertionError: Expected to find '/report_result?exit:0
' in '//report_result?abort:Assertion failed: abs(m->x-10) <= 1 && abs(m->y-20) <= 1 && abs(m->xrel-10) <= 1 && abs(m->yrel-20) <= 1, at: /root/project/test/browser/test_sdl_mouse.c,32,one
', diff:

--- expected
+++ actual
@@ -1 +1 @@
-/report_result?exit:0
+//report_result?abort:Assertion failed: abs(m->x-10) <= 1 && abs(m->y-20) <= 1 && abs(m->xrel-10) <= 1 && abs(m->yrel-20) <= 1, at: /root/project/test/browser/test_sdl_mouse.c,32,one



During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/root/project/test/test_browser.py", line 1070, in test_sdl_mouse
    self.btest_exit('test_sdl_mouse.c', emcc_args=['-O2', '--minify=0', '--pre-js', test_file('browser/fake_events.js'), '-lSDL', '-lGL'])
  File "/root/project/test/common.py", line 2404, in btest_exit
    return self.btest(filename, *args, **kwargs)
  File "/root/project/test/common.py", line 2433, in btest
    self.run_browser(outfile + url_suffix, expected=['/report_result?' + e for e in expected], timeout=timeout, extra_tries=extra_tries)
  File "/root/project/test/common.py", line 2358, in run_browser
    return self.run_browser(html_file, expected, message, timeout, extra_tries - 1)
  File "/root/project/test/common.py", line 2360, in run_browser
    raise e
  File "/root/project/test/common.py", line 2353, in run_browser
    self.assertContained(expected, output)
  File "/root/project/test/common.py", line 1652, in assertContained
    self.fail("Expected to find '%s' in '%s', diff:\n\n%s\n%s" % (
AssertionError: Expected to find '/report_result?exit:0
' in '//report_result?abort:Assertion failed: abs(m->x-10) <= 1 && abs(m->y-20) <= 1 && abs(m->xrel-10) <= 1 && abs(m->yrel-20) <= 1, at: /root/project/test/browser/test_sdl_mouse.c,32,one
', diff:

--- expected
+++ actual
@@ -1 +1 @@
-/report_result?exit:0
+//report_result?abort:Assertion failed: abs(m->x-10) <= 1 && abs(m->y-20) <= 1 && abs(m->xrel-10) <= 1 && abs(m->yrel-20) <= 1, at: /root/project/test/browser/test_sdl_mouse.c,32,one

[sbc100]

The test_sdl_mouse is a know flake that has been happening for a few days now.