Stop exporting systemserverclasspath_fragment when targeting S

Previously, when targeting the S release the generated sdk snapshot
would contain prebuilt_systemserverclasspath_fragment modules even
though they were only added in T.

This allows SdkMemberTypes to specify the set of target build releases
they support and ignores them when targeting an unsupported target
build release.

Test: m nothing
      packages/modules/common/build/mainline_modules_sdks.sh
      # Check that the for-S-build snapshots do not include SSCPFs.
Bug: 237718221
Change-Id: I2df08c2fcebf9b866695d691572a9d3783758b17

android/sdk.go

@@ -661,6 +661,10 @@ type SdkMemberType interface {
 	// an Android.bp file.
 	RequiresBpProperty() bool
 
+	// SupportedBuildReleases returns the string representation of a set of target build releases that
+	// support this member type.
+	SupportedBuildReleases() string
+
 	// UsableWithSdkAndSdkSnapshot returns true if the member type supports the sdk/sdk_snapshot,
 	// false otherwise.
 	UsableWithSdkAndSdkSnapshot() bool
@@ -773,6 +777,11 @@ type SdkMemberTypeBase struct {
 	// property to be specifiable in an Android.bp file.
 	BpPropertyNotRequired bool
 
+	// The name of the first targeted build release.
+	//
+	// If not specified then it is assumed to be available on all targeted build releases.
+	SupportedBuildReleaseSpecification string
+
 	SupportsSdk     bool
 	HostOsDependent bool
 
@@ -793,6 +802,10 @@ func (b *SdkMemberTypeBase) RequiresBpProperty() bool {
 	return !b.BpPropertyNotRequired
 }
 
+func (b *SdkMemberTypeBase) SupportedBuildReleases() string {
+	return b.SupportedBuildReleaseSpecification
+}
+
 func (b *SdkMemberTypeBase) UsableWithSdkAndSdkSnapshot() bool {
 	return b.SupportsSdk
 }