Add version 1.9.21 of kotlinc to third-party dependencneis

Contents of README.google:
Name: Kotlin
URL: https://github.com/JetBrains/kotlin/releases/download/v1.9.21/kotlin-compiler-1.9.21.zip
Version: 1.9.21
Revision: NA
License: Apache License Version 2.0

Bug: b/315458778
Change-Id: I7e1bff0e057ea9d7c607919830ecadfb819c935a
diff --git a/.gitignore b/.gitignore
index 3da002f..1c8e875 100644
--- a/.gitignore
+++ b/.gitignore
@@ -164,6 +164,8 @@
 third_party/kotlin/kotlin-compiler-1.7.0
 third_party/kotlin/kotlin-compiler-1.8.0.tar.gz
 third_party/kotlin/kotlin-compiler-1.8.0
+third_party/kotlin/kotlin-compiler-1.9.21.tar.gz
+third_party/kotlin/kotlin-compiler-1.9.21
 third_party/kotlin/kotlin-compiler-dev.tar.gz
 third_party/kotlin/kotlin-compiler-dev
 third_party/kotlinx-coroutines-1.3.6.tar.gz
diff --git a/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt b/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
index 418e0d5..56562ac 100644
--- a/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
+++ b/d8_r8/commonBuildSrc/src/main/kotlin/DependenciesPlugin.kt
@@ -707,6 +707,7 @@
     "kotlin-compiler-1.6.0",
     "kotlin-compiler-1.7.0",
     "kotlin-compiler-1.8.0",
+    "kotlin-compiler-1.9.21",
     "kotlin-compiler-dev")
     .map { ThirdPartyDependency(
       it,
diff --git a/third_party/kotlin/kotlin-compiler-1.9.21.tar.gz.sha1 b/third_party/kotlin/kotlin-compiler-1.9.21.tar.gz.sha1
new file mode 100644
index 0000000..8e93ad6
--- /dev/null
+++ b/third_party/kotlin/kotlin-compiler-1.9.21.tar.gz.sha1
@@ -0,0 +1 @@
+17c6c5c9cefab179553adaaf860c86e4e598a002
\ No newline at end of file