Make crates depending on proc-macro host-only

These crates are used to generate Rust source, and do not belong on the
device.

Test: m checkbuild
Change-Id: Ied561fe3543841e5fb3f5762f1d1469d317e3426
diff --git a/Android.bp b/Android.bp
index 13c7d88..df5e2a6 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,8 +1,7 @@
 // This file is generated by cargo2android.py.
 
-rust_library_rlib {
+rust_library_host_rlib {
     name: "libproc_macro2",
-    host_supported: true,
     crate_name: "proc_macro2",
     srcs: ["src/lib.rs"],
     edition: "2018",
@@ -20,9 +19,8 @@
     ],
 }
 
-rust_test {
+rust_test_host {
     name: "proc-macro2_test_src_lib",
-    host_supported: true,
     crate_name: "proc_macro2",
     srcs: ["src/lib.rs"],
     relative_install_path: "rust/proc-macro2",
@@ -42,9 +40,8 @@
     ],
 }
 
-rust_test {
+rust_test_host {
     name: "proc-macro2_tests_test",
-    host_supported: true,
     crate_name: "proc_macro2",
     srcs: [
         "tests/features.rs",