Add support for PRODUCT_RELEASE_CONFIG_MAPS

This allows product config to determine what build flags are present in
a product's build, as well as their value.

As product config moves to a declarative specification, this can be
handled with less unnecessary work.

Bug: b/302593603
Bug: b/308849337
Test: manual
Change-Id: If57622059bb7d1c33df7498321db621c0c2d30c0

ui/build/config.go

@@ -31,6 +31,7 @@ import (
 	"time"
 
 	"android/soong/shared"
+	"android/soong/ui/metrics"
 
 	"google.golang.org/protobuf/proto"
 
@@ -465,6 +466,42 @@ func NewBuildActionConfig(action BuildAction, dir string, ctx Context, args ...s
 	return NewConfig(ctx, getConfigArgs(action, dir, ctx, args)...)
 }
 
+// Prepare for getting make variables.  For them to be accurate, we need to have
+// obtained PRODUCT_RELEASE_CONFIG_MAPS.
+//
+// Returns:
+//
+//	Whether config should be called again.
+//
+// TODO: when converting product config to a declarative language, make sure
+// that PRODUCT_RELEASE_CONFIG_MAPS is properly handled as a separate step in
+// that process.
+func SetProductReleaseConfigMaps(ctx Context, config Config) bool {
+	ctx.BeginTrace(metrics.RunKati, "SetProductReleaseConfigMaps")
+	defer ctx.EndTrace()
+
+	if config.SkipConfig() {
+		// This duplicates the logic from Build to skip product config
+		// if the user has explicitly said to.
+		return false
+	}
+
+	releaseConfigVars := []string{
+		"PRODUCT_RELEASE_CONFIG_MAPS",
+	}
+
+	origValue, _ := config.environ.Get("PRODUCT_RELEASE_CONFIG_MAPS")
+	// Get the PRODUCT_RELEASE_CONFIG_MAPS for this product, to avoid polluting the environment
+	// when we run product config to get the rest of the make vars.
+	releaseMapVars, err := dumpMakeVars(ctx, config, nil, releaseConfigVars, false, "")
+	if err != nil {
+		ctx.Fatalln("Error getting PRODUCT_RELEASE_CONFIG_MAPS:", err)
+	}
+	productReleaseConfigMaps := releaseMapVars["PRODUCT_RELEASE_CONFIG_MAPS"]
+	os.Setenv("PRODUCT_RELEASE_CONFIG_MAPS", productReleaseConfigMaps)
+	return origValue != productReleaseConfigMaps
+}
+
 // storeConfigMetrics selects a set of configuration information and store in
 // the metrics system for further analysis.
 func storeConfigMetrics(ctx Context, config Config) {

ui/build/dumpvars.go

@@ -191,6 +191,9 @@ func runMakeProductConfig(ctx Context, config Config) {
 		"TARGET_BUILD_APPS",
 		"TARGET_BUILD_UNBUNDLED",
 
+		// Additional release config maps
+		"PRODUCT_RELEASE_CONFIG_MAPS",
+
 		// compiler wrappers set up by make
 		"CC_WRAPPER",
 		"CXX_WRAPPER",