Add product_config module

product_config module will export productVariables struct (defined in
android/variable.go). Other modules can depend on product_Config module
to read product variables, without needing to update Soong.

Bug: 346214955
Test: build and see output of product_config module
Change-Id: I06e1d2716dc2a8b90984bb46c5fc901cd1ca5020
diff --git a/ui/build/config.go b/ui/build/config.go
index feded1c..a217d48 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -1488,6 +1488,15 @@
 	}
 }
 
+func (c *configImpl) SoongExtraVarsFile() string {
+	targetProduct, err := c.TargetProductOrErr()
+	if err != nil {
+		return filepath.Join(c.SoongOutDir(), "soong.extra.variables")
+	} else {
+		return filepath.Join(c.SoongOutDir(), "soong."+targetProduct+".extra.variables")
+	}
+}
+
 func (c *configImpl) SoongNinjaFile() string {
 	targetProduct, err := c.TargetProductOrErr()
 	if err != nil {
diff --git a/ui/build/soong.go b/ui/build/soong.go
index 2f3150d..99474d9 100644
--- a/ui/build/soong.go
+++ b/ui/build/soong.go
@@ -694,6 +694,7 @@
 		}
 	}
 	distFile(ctx, config, config.SoongVarsFile(), "soong")
+	distFile(ctx, config, config.SoongExtraVarsFile(), "soong")
 
 	if !config.SkipKati() {
 		distGzipFile(ctx, config, config.SoongAndroidMk(), "soong")
diff --git a/ui/build/test_build.go b/ui/build/test_build.go
index 24ad082..687ad6f 100644
--- a/ui/build/test_build.go
+++ b/ui/build/test_build.go
@@ -64,7 +64,8 @@
 	outDir := config.OutDir()
 	modulePathsDir := filepath.Join(outDir, ".module_paths")
 	rawFilesDir := filepath.Join(outDir, "soong", "raw")
-	variablesFilePath := filepath.Join(outDir, "soong", "soong.variables")
+	variablesFilePath := config.SoongVarsFile()
+	extraVariablesFilePath := config.SoongExtraVarsFile()
 
 	// dexpreopt.config is an input to the soong_docs action, which runs the
 	// soong_build primary builder. However, this file is created from $(shell)
@@ -95,6 +96,7 @@
 		if strings.HasPrefix(line, modulePathsDir) ||
 			strings.HasPrefix(line, rawFilesDir) ||
 			line == variablesFilePath ||
+			line == extraVariablesFilePath ||
 			line == dexpreoptConfigFilePath ||
 			line == buildDatetimeFilePath ||
 			line == bpglob ||