Export build flags to soong.

This exports a map of build flags used in this release config to Soong.

Bug: 302514918
Test: manual
Change-Id: Id95c03e14cfbb91c0cb9c8c37a065b8387733317

android/config.go

@@ -2124,3 +2124,8 @@ func (c *deviceConfig) ReleaseExposeFlaggedApi() bool {
 func (c *deviceConfig) HideFlaggedApis() bool {
 	return c.NextReleaseHideFlaggedApi() && !c.ReleaseExposeFlaggedApi()
 }
+
+func (c *config) GetBuildFlag(name string) (string, bool) {
+	val, ok := c.productVariables.BuildFlags[name]
+	return val, ok
+}

android/variable.go

@@ -492,6 +492,8 @@ type ProductVariables struct {
 	NextReleaseHideFlaggedApi *bool `json:",omitempty"`
 
 	Release_expose_flagged_api *bool `json:",omitempty"`
+
+	BuildFlags map[string]string `json:",omitempty"`
 }
 
 type PartitionQualifiedVariablesType struct {