config/pipeline: enable android tree and build configs

Monitor linux `android` tree. Add build configs for `android-mainline`
branch.

Signed-off-by: Helen Koike <[email protected]>

Author: Helen Koike

config/pipeline.yaml

@@ -286,6 +286,9 @@ trees:
   mediatek:
     url: 'https://git.kernel.org/pub/scm/linux/kernel/git/mediatek/linux.git'
 
+  android:
+    url: 'https://android.googlesource.com/kernel/common'
+
 platforms:
 
   docker:
@@ -593,3 +596,8 @@ build_configs:
     tree: mediatek
     branch: 'for-next'
     variants: *build-variants
+
+  android_mainline:
+    tree: android
+    branch: 'android-mainline'
+    variants: *build-variants