rust: Support new rust_stdlib_prebuilt_host type

Refactor Rust prebuilts to support the new rust_stdlib_prebuilt_host
module type, and change the format for depending on the prebuilt host
stdlibs.

Bug: 140642453
Test: m
Change-Id: Ifbc4741818777934e917631c788b20911856c44a
diff --git a/rust/androidmk.go b/rust/androidmk.go
index 7eb5dbd..c9f6486 100644
--- a/rust/androidmk.go
+++ b/rust/androidmk.go
@@ -147,6 +147,7 @@
 			}
 		})
 }
+
 func (procMacro *procMacroDecorator) AndroidMk(ctx AndroidMkContext, ret *android.AndroidMkEntries) {
 	ctx.SubAndroidMk(ret, procMacro.baseCompiler)