compiler: make it easier to apply breaking changes to std.builtin

Documentation for this will be on the wiki shortly.

Resolves: #21842

stage1/config.zig.in

@@ -13,3 +13,4 @@ pub const value_tracing = false;
 pub const skip_non_native = false;
 pub const force_gpa = false;
 pub const dev = .core;
+pub const value_interpret_mode = .direct;