No need to reserve build_ because we use build. instead.
diff --git a/mesonbuild/optinterpreter.py b/mesonbuild/optinterpreter.py
index 1d0533e..8feb4f3 100644
--- a/mesonbuild/optinterpreter.py
+++ b/mesonbuild/optinterpreter.py
@@ -23,7 +23,7 @@
forbidden_option_names = set(coredata.builtin_options.keys())
forbidden_prefixes = [lang + '_' for lang in compilers.all_languages] + ['b_', 'backend_']
-reserved_prefixes = ['cross_', 'build_']
+reserved_prefixes = ['cross_']
def is_invalid_name(name: str, *, log: bool = True) -> bool:
if name in forbidden_option_names:
