diff --git a/android/arch.go b/android/arch.go
index 922548e..e440486 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -596,7 +596,7 @@
 }()
 
 var (
-	osTypeList      []OsType
+	OsTypeList      []OsType
 	commonTargetMap = make(map[string]Target)
 
 	NoOsType    OsType
@@ -672,7 +672,7 @@
 
 		DefaultDisabled: defDisabled,
 	}
-	osTypeList = append(osTypeList, os)
+	OsTypeList = append(OsTypeList, os)
 
 	if _, found := commonTargetMap[name]; found {
 		panic(fmt.Errorf("Found Os type duplicate during OsType registration: %q", name))
@@ -684,7 +684,7 @@
 }
 
 func osByName(name string) OsType {
-	for _, os := range osTypeList {
+	for _, os := range OsTypeList {
 		if os.Name == name {
 			return os
 		}
@@ -750,7 +750,7 @@
 
 	var moduleOSList []OsType
 
-	for _, os := range osTypeList {
+	for _, os := range OsTypeList {
 		supportedClass := false
 		for _, osClass := range osClasses {
 			if os.Class == osClass {
@@ -1071,7 +1071,7 @@
 			"Arm_on_x86",
 			"Arm_on_x86_64",
 		}
-		for _, os := range osTypeList {
+		for _, os := range OsTypeList {
 			targets = append(targets, os.Field)
 
 			for _, archType := range osArchTypeMap[os] {
diff --git a/android/sdk.go b/android/sdk.go
index f28c392..969e21a 100644
--- a/android/sdk.go
+++ b/android/sdk.go
@@ -448,10 +448,29 @@
 
 // Base structure for all implementations of SdkMemberProperties.
 //
-// Contains common properties that apply across many different member types.
+// Contains common properties that apply across many different member types. These
+// are not affected by the optimization to extract common values.
 type SdkMemberPropertiesBase struct {
 	// The setting to use for the compile_multilib property.
 	Compile_multilib string
+
+	// The number of unique os types supported by the member variants.
+	Os_count int
+
+	// The os type for which these properties refer.
+	Os OsType
+}
+
+// The os prefix to use for any file paths in the sdk.
+//
+// Is an empty string if the member only provides variants for a single os type, otherwise
+// is the OsType.Name.
+func (b *SdkMemberPropertiesBase) OsPrefix() string {
+	if b.Os_count == 1 {
+		return ""
+	} else {
+		return b.Os.Name
+	}
 }
 
 func (b *SdkMemberPropertiesBase) Base() *SdkMemberPropertiesBase {