Use Config/DeviceConfig functions to access ProductVariables

An upcoming change will stop exporting ProductVariables from Config, so
switch to using existing accessor functions, and add more when they're
missing.

Bug: 76168832
Test: out/soong/build.ninja is identical
Change-Id: Ie0135bdbd2df3258ef3ddb53e5f8fc00aa9b97f7
diff --git a/android/makevars.go b/android/makevars.go
index b6cd571..3792357 100644
--- a/android/makevars.go
+++ b/android/makevars.go
@@ -36,6 +36,7 @@
 // Interface for other packages to use to declare make variables
 type MakeVarsContext interface {
 	Config() Config
+	DeviceConfig() DeviceConfig
 	SingletonContext() SingletonContext
 
 	// Verify the make variable matches the Soong version, fail the build
@@ -231,6 +232,10 @@
 	return c.config
 }
 
+func (c *makeVarsContext) DeviceConfig() DeviceConfig {
+	return DeviceConfig{c.config.deviceConfig}
+}
+
 func (c *makeVarsContext) SingletonContext() SingletonContext {
 	return c.ctx
 }