Support installable prebuilt jars

Some host modules need to be installed.  Add an installable property.

Test: m checkbuild
Change-Id: Ifd023213ff66e81aa77ba1741c75837a1dd88d1d

java/androidmk.go

@@ -74,7 +74,7 @@ func (prebuilt *Import) AndroidMk() android.AndroidMkData {
 		Include:    "$(BUILD_SYSTEM)/soong_java_prebuilt.mk",
 		Extra: []android.AndroidMkExtraFunc{
 			func(w io.Writer, outputFile android.Path) {
-				fmt.Fprintln(w, "LOCAL_UNINSTALLABLE_MODULE := true")
+				fmt.Fprintln(w, "LOCAL_UNINSTALLABLE_MODULE := ", !proptools.Bool(prebuilt.properties.Installable))
 				fmt.Fprintln(w, "LOCAL_SOONG_HEADER_JAR :=", prebuilt.combinedClasspathFile.String())
 				fmt.Fprintln(w, "LOCAL_SDK_VERSION :=", prebuilt.properties.Sdk_version)
 			},

java/java.go

@@ -920,6 +920,8 @@ type ImportProperties struct {
 	Jars []string
 
 	Sdk_version string
+
+	Installable *bool
 }
 
 type Import struct {