Rename modulesAddedWall to modulesWarningsAllowed

MODULES_ADDED_WALL is deceiving and it actually meant which modules are
allowed to have warnings (do not automatically append -Werror flag).

Test: presubmit
Bug: 233183337
Change-Id: Ibd21e269eba04d01f13026d70a9e34ccb1cf26d7
diff --git a/cc/compiler.go b/cc/compiler.go
index 49b6fba..773a642 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -589,7 +589,7 @@
 			addToModuleList(ctx, modulesUsingWnoErrorKey, module)
 		} else if !inList("-Werror", flags.Local.CFlags) && !inList("-Werror", flags.Local.CppFlags) {
 			if warningsAreAllowed(ctx.ModuleDir()) {
-				addToModuleList(ctx, modulesAddedWallKey, module)
+				addToModuleList(ctx, modulesWarningsAllowedKey, module)
 			} else {
 				flags.Local.CFlags = append([]string{"-Werror"}, flags.Local.CFlags...)
 			}