Use the `arm64` variant of JDK on M1 Macbook Pro.

Test: Tested the script locally.
Change-Id: I7b684d6a791cc67896702154e5bde7c7cd50c4e0
diff --git a/gradlew b/gradlew
index 62c3e5e..910d151 100755
--- a/gradlew
+++ b/gradlew
@@ -83,7 +83,11 @@
     msys=true
     ;;
 esac
-
+platform_suffix="x86"
+case "$(arch)" in
+  arm64* )
+    platform_suffix="arm64"
+esac
 # Attempt to set APP_HOME
 # Resolve links: $0 may be a link
 PRG="$0"
@@ -118,7 +122,7 @@
 # setup from each lint module.
 export ANDROID_HOME="$APP_HOME/../../prebuilts/fullsdk-$plat"
 # override JAVA_HOME, because CI machines have it and it points to very old JDK
-export JAVA_HOME="$APP_HOME/../../prebuilts/jdk/jdk11/$plat-x86"
+export JAVA_HOME="$APP_HOME/../../prebuilts/jdk/jdk11/$plat-$platform_suffix"
 export JAVA_TOOLS_JAR="$APP_HOME/../../prebuilts/jdk/jdk8/$plat-x86/lib/tools.jar"
 export STUDIO_GRADLE_JDK=$JAVA_HOME