Add support for downloading kotlin dev compilers

Contents of README.google:
Name: Kotlin
URL: https://github.com/JetBrains/kotlin/
Version: 1.5.0
Revision: NA
License: Apache License Version 2.0

Bug: 200582899
Change-Id: I9285f3026c171ce4954166a19fb7de83cf6e2341
diff --git a/.gitignore b/.gitignore
index 080826a..7a9429b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -114,6 +114,8 @@
 third_party/kotlin/kotlin-compiler-1.4.20
 third_party/kotlin/kotlin-compiler-1.5.0.tar.gz
 third_party/kotlin/kotlin-compiler-1.5.0
+third_party/kotlin/kotlin-compiler-dev.tar.gz
+third_party/kotlin/kotlin-compiler-dev
 third_party/kotlinx-coroutines-1.3.6.tar.gz
 third_party/kotlinx-coroutines-1.3.6
 third_party/nest/*