coredata: remove get_builtin_options

This returns a list out of th keys of a dict. In both cases of use
remaining though it's used for checking membership, checking for list
membership, lists are O(n) lookup, while dicts are O(1), so removing
the abstraction reduces typing and improves performance.

mesonbuild/coredata.py

@@ -508,7 +508,7 @@ class CoreData:
             if subproject:
                 if not k.startswith(subproject + ':'):
                     continue
-            elif k not in get_builtin_options():
+            elif k not in builtin_options:
                 if ':' in k:
                     continue
                 if optinterpreter.is_invalid_name(k):
@@ -654,11 +654,8 @@ def save(obj, build_dir):
     os.replace(tempfilename, filename)
     return filename
 
-def get_builtin_options():
-    return list(builtin_options.keys())
-
 def is_builtin_option(optname):
-    return optname in get_builtin_options()
+    return optname in builtin_options
 
 def get_builtin_option_choices(optname):
     if is_builtin_option(optname):

mesonbuild/optinterpreter.py

@@ -20,7 +20,7 @@ from . import coredata
 from . import mesonlib
 from . import compilers
 
-forbidden_option_names = coredata.get_builtin_options()
+forbidden_option_names = set(coredata.builtin_options.keys())
 forbidden_prefixes = [lang + '_' for lang in compilers.all_languages] + ['b_', 'backend_']
 reserved_prefixes = ['cross_']