Use the current java version for -jvm-target

This is a partial revert of aosp/541879.
In that cl, the kotlin jvm version was always
set to 1.8 because that's what the kotlin
complier supported at the time, but now
it supports more versions:

$ ./external/kotlinc/bin/kotlinc -jvm-target foo
error: unknown JVM target version: foo
Supported versions: 1.6, 1.8, 9, 10, 11, 12, 13, 14, 15, 16, 17

Bug: 69160377
Bug: 236431222
Test: Treehugger
Change-Id: I273e0b4d1f484013889e17c60bc1b299a3f975a1

java/java.go

@@ -526,6 +526,20 @@ func (v javaVersion) String() string {
 	}
 }
 
+func (v javaVersion) StringForKotlinc() string {
+	// $ ./external/kotlinc/bin/kotlinc -jvm-target foo
+	// error: unknown JVM target version: foo
+	// Supported versions: 1.6, 1.8, 9, 10, 11, 12, 13, 14, 15, 16, 17
+	switch v {
+	case JAVA_VERSION_7:
+		return "1.6"
+	case JAVA_VERSION_9:
+		return "9"
+	default:
+		return v.String()
+	}
+}
+
 // Returns true if javac targeting this version uses system modules instead of a bootclasspath.
 func (v javaVersion) usesJavaModules() bool {
 	return v >= 9

java/kotlin.go

@@ -119,8 +119,7 @@ func kotlinCompile(ctx android.ModuleContext, outputFile, headerOutputFile andro
 			"srcJarDir":         android.PathForModuleOut(ctx, "kotlinc", "srcJars").String(),
 			"kotlinBuildFile":   android.PathForModuleOut(ctx, "kotlinc-build.xml").String(),
 			"emptyDir":          android.PathForModuleOut(ctx, "kotlinc", "empty").String(),
-			// http://b/69160377 kotlinc only supports -jvm-target 1.6 and 1.8
+			"kotlinJvmTarget":   flags.javaVersion.StringForKotlinc(),
-			"kotlinJvmTarget": "1.8",
 			"name":              kotlinName,
 		},
 	})