Support installable prebuilt jars

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

Test: m checkbuild
Change-Id: Ifd023213ff66e81aa77ba1741c75837a1dd88d1d
diff --git a/java/androidmk.go b/java/androidmk.go
index c61b7e5..d3aadef 100644
--- a/java/androidmk.go
+++ b/java/androidmk.go
@@ -74,7 +74,7 @@
 		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)
 			},
diff --git a/java/java.go b/java/java.go
index 497b285..fbd7bdd 100644
--- a/java/java.go
+++ b/java/java.go
@@ -920,6 +920,8 @@
 	Jars []string
 
 	Sdk_version string
+
+	Installable *bool
 }
 
 type Import struct {