Turn on warnings for ToT aidl_interfaces

"-Weverything" is passed to the AIDL compiler.

Bug: 177608683
Test: m
Change-Id: I6db01a6e53b66031cd143f695f65083530237be7
diff --git a/build/aidl_interface_backends.go b/build/aidl_interface_backends.go
index 8c85c2a..d4ae2f8 100644
--- a/build/aidl_interface_backends.go
+++ b/build/aidl_interface_backends.go
@@ -84,7 +84,7 @@
 		GenTrace:   genTrace,
 		Unstable:   i.properties.Unstable,
 		Visibility: srcsVisibility(mctx, lang),
-		Flags:      i.properties.Flags,
+		Flags:      i.flagsForAidlGenRule(version),
 	})
 
 	importExportDependencies := []string{}
@@ -240,7 +240,7 @@
 		GenTrace:   proptools.Bool(i.properties.Gen_trace),
 		Unstable:   i.properties.Unstable,
 		Visibility: srcsVisibility(mctx, langJava),
-		Flags:      i.properties.Flags,
+		Flags:      i.flagsForAidlGenRule(version),
 	})
 
 	mctx.CreateModule(aidlImplementationGeneratorFactory, &nameProperties{
@@ -287,7 +287,7 @@
 		Version:    i.versionForAidlGenRule(version),
 		Unstable:   i.properties.Unstable,
 		Visibility: srcsVisibility(mctx, langRust),
-		Flags:      i.properties.Flags,
+		Flags:      i.flagsForAidlGenRule(version),
 	})
 
 	versionedRustName := fixRustName(i.versionedName(version))
@@ -363,6 +363,15 @@
 	return version
 }
 
+func (i *aidlInterface) flagsForAidlGenRule(version string) (flags []string) {
+	flags = append(flags, i.properties.Flags...)
+	// For ToT, turn on "-Weverything" (enable all warnings)
+	if version == i.nextVersion() {
+		flags = append(flags, "-Weverything")
+	}
+	return
+}
+
 func (i *aidlInterface) isModuleForVndk(version string) bool {
 	// TODO(b/150578172) remove exception when every module specify its version.
 	version = i.normalizeVersion(version)