Merge "Handle -Cflag syntax and use prebuilt cargo." am: b517b4614d am: a321869ef5 am: 21480a98b1 am: 8cd4acaa36

Original change: https://android-review.googlesource.com/c/platform/development/+/1371298

Change-Id: I6d7878c1d6b55ac59c9dba48a513f0ef6fc0c995