v.gen.c: do not use precomputed const values in -usecache mode (fix `v test-all` on M1)

vlib/v/gen/c/cgen.v

@@ -4905,11 +4905,13 @@ fn (mut g Gen) const_decl(node ast.ConstDecl) {
 				}
 			}
 			else {
+				if g.pref.build_mode != .build_module {
 					if ct_value := field.comptime_expr_value() {
 						if g.const_decl_precomputed(field.mod, name, ct_value, field.typ) {
 							continue
 						}
 					}
+				}
 				if field.is_simple_define_const() {
 					// "Simple" expressions are not going to need multiple statements,
 					// only the ones which are inited later, so it's safe to use expr_string