SCons: Format buildsystem files with psf/black

Configured for a max line length of 120 characters.

psf/black is very opinionated and purposely doesn't leave much room for
configuration. The output is mostly OK so that should be fine for us,
but some things worth noting:

- Manually wrapped strings will be reflowed, so by using a line length
  of 120 for the sake of preserving readability for our long command
  calls, it also means that some manually wrapped strings are back on
  the same line and should be manually merged again.

- Code generators using string concatenation extensively look awful,
  since black puts each operand on a single line. We need to refactor
  these generators to use more pythonic string formatting, for which
  many options are available (`%`, `format` or f-strings).

- CI checks and a pre-commit hook will be added to ensure that future
  buildsystem changes are well-formatted.

modules/mono/config.py

@@ -3,41 +3,52 @@ def can_build(env, platform):
 
 
 def configure(env):
-    if env['platform'] not in ['windows', 'osx', 'linuxbsd', 'server', 'android', 'haiku', 'javascript']:
-        raise RuntimeError('This module does not currently support building for this platform')
+    if env["platform"] not in ["windows", "osx", "linuxbsd", "server", "android", "haiku", "javascript"]:
+        raise RuntimeError("This module does not currently support building for this platform")
 
     env.use_ptrcall = True
-    env.add_module_version_string('mono')
+    env.add_module_version_string("mono")
 
     from SCons.Script import BoolVariable, PathVariable, Variables, Help
 
     envvars = Variables()
-    envvars.Add(PathVariable('mono_prefix', 'Path to the mono installation directory for the target platform and architecture', '', PathVariable.PathAccept))
-    envvars.Add(BoolVariable('mono_static', 'Statically link mono', False))
-    envvars.Add(BoolVariable('mono_glue', 'Build with the mono glue sources', True))
-    envvars.Add(BoolVariable('copy_mono_root', 'Make a copy of the mono installation directory to bundle with the editor', False))
-    envvars.Add(BoolVariable('xbuild_fallback', 'If MSBuild is not found, fallback to xbuild', False))
+    envvars.Add(
+        PathVariable(
+            "mono_prefix",
+            "Path to the mono installation directory for the target platform and architecture",
+            "",
+            PathVariable.PathAccept,
+        )
+    )
+    envvars.Add(BoolVariable("mono_static", "Statically link mono", False))
+    envvars.Add(BoolVariable("mono_glue", "Build with the mono glue sources", True))
+    envvars.Add(
+        BoolVariable(
+            "copy_mono_root", "Make a copy of the mono installation directory to bundle with the editor", False
+        )
+    )
+    envvars.Add(BoolVariable("xbuild_fallback", "If MSBuild is not found, fallback to xbuild", False))
     envvars.Update(env)
     Help(envvars.GenerateHelpText(env))
 
-    if env['platform'] == 'javascript':
+    if env["platform"] == "javascript":
         # Mono wasm already has zlib builtin, so we need this workaround to avoid symbol collisions
-        print('Compiling with Mono wasm disables \'builtin_zlib\'')
-        env['builtin_zlib'] = False
+        print("Compiling with Mono wasm disables 'builtin_zlib'")
+        env["builtin_zlib"] = False
         thirdparty_zlib_dir = "#thirdparty/zlib/"
         env.Prepend(CPPPATH=[thirdparty_zlib_dir])
 
 
 def get_doc_classes():
     return [
-        '@C#',
-        'CSharpScript',
-        'GodotSharp',
+        "@C#",
+        "CSharpScript",
+        "GodotSharp",
     ]
 
 
 def get_doc_path():
-    return 'doc_classes'
+    return "doc_classes"
 
 
 def is_enabled():