Clean up srcjar directories after each rule

The srcjar directories just confuse people looking for generated
files, clean them up after each rule.

Test: m checkbuild
Change-Id: If712ce7d4922619fd8420ae8f89830fe7824114d
diff --git a/java/kotlin.go b/java/kotlin.go
index 9c47f98..81b89f9 100644
--- a/java/kotlin.go
+++ b/java/kotlin.go
@@ -32,7 +32,8 @@
 			`${config.GenKotlinBuildFileCmd} $classpath $classesDir $out.rsp $srcJarDir/list > $kotlinBuildFile &&` +
 			`${config.KotlincCmd} ${config.JavacHeapFlags} $kotlincFlags ` +
 			`-jvm-target $kotlinJvmTarget -Xbuild-file=$kotlinBuildFile && ` +
-			`${config.SoongZipCmd} -jar -o $out -C $classesDir -D $classesDir`,
+			`${config.SoongZipCmd} -jar -o $out -C $classesDir -D $classesDir && ` +
+			`rm -rf "$srcJarDir"`,
 		CommandDeps: []string{
 			"${config.KotlincCmd}",
 			"${config.KotlinCompilerJar}",
@@ -89,7 +90,8 @@
 			`$kaptProcessorPath ` +
 			`$kaptProcessor ` +
 			`-Xbuild-file=$kotlinBuildFile && ` +
-			`${config.SoongZipCmd} -jar -o $out -C $kaptDir/sources -D $kaptDir/sources`,
+			`${config.SoongZipCmd} -jar -o $out -C $kaptDir/sources -D $kaptDir/sources && ` +
+			`rm -rf "$srcJarDir"`,
 		CommandDeps: []string{
 			"${config.KotlincCmd}",
 			"${config.KotlinCompilerJar}",