Mark sysroots vendor_available

As part of adding vendor support for Rust static libraries, we need to
make the sysroots (the rlib variants at least) vendor available.

Bug: 172525289
Test: New Soong tests pass
Test: Example vendor cc_binary links against rust_ffi_static module.
Change-Id: Ib2255c9ae11c670bd239fa0051f3fb6f85717e85
1 file changed
tree: caf48912474db98520949380b1f3d11c40993f66
  1. bootstrap/
  2. darwin-x86/
  3. linux-x86/
  4. Android.bp
  5. OWNERS