Add android_sdk_repo_host to build platform-tools&build-tools

The Android SDK has been built with Make up until now, monolithically,
then split up into several sdk-repo zip files for different purposes.
The Mac and Windows SDKs really only need to contain the platform-tools
and build-tools pieces, but due to this monolithic sdk zip, we had to
build the whole SDK first.

This adds an `android_sdk_repo_host` module that can build these
platform-tools and build-tools zips.

Bug: 187222815
Change-Id: I55809e1d7447dd65e22461f921b2b8abb6d5f822
diff --git a/android/androidmk.go b/android/androidmk.go
index 967c550..feaef1f 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -836,6 +836,7 @@
 		case "*aidl.aidlApi": // writes non-custom before adding .phony
 		case "*aidl.aidlMapping": // writes non-custom before adding .phony
 		case "*android.customModule": // appears in tests only
+		case "*android_sdk.sdkRepoHost": // doesn't go through base_rules
 		case "*apex.apexBundle": // license properties written
 		case "*bpf.bpf": // license properties written (both for module and objs)
 		case "*genrule.Module": // writes non-custom before adding .phony