Move NDK ABI monitoring enabling flag to release flags

Currently NDK ABI monitoring is enabled by switching boolean flag in
soong code. When this flag is switched, it will enable ABI monitoring in
all release configurations at once.

This change moves the flag from soong code to the trunk-stable flags
framework ("build/release/build_flags.scl") that allows to enable it
only in specific configurations like "trunk-staging".

Test: TH
Bug: 156513478
Change-Id: Ibb810a834c0d756b22782b1a2d8ec5a5e575a4b3

android/config.go

@@ -239,6 +239,11 @@ func (c Config) ReleaseDefaultModuleBuildFromSource() bool {
 		Bool(c.config.productVariables.ReleaseDefaultModuleBuildFromSource)
 }
 
+// Enables ABI monitoring of NDK libraries
+func (c Config) ReleaseNdkAbiMonitored() bool {
+	return c.config.productVariables.GetBuildFlagBool("RELEASE_NDK_ABI_MONITORED")
+}
+
 // A DeviceConfig object represents the configuration for a particular device
 // being built. For now there will only be one of these, but in the future there
 // may be multiple devices being built.