Add Rust fuzzing support.

Add a rust_fuzz module which builds a libfuzzer binary that enabes
asan+sancov. This relies on the libfuzzer-sys crate.

Bug: 147140513
Test: Local rust_fuzz example builds, fuzzes with asan+sancov.
Change-Id: I57db3b8d25869791824ccfab768d13b0bb9d42fa

rust/compiler.go

@@ -146,6 +146,7 @@ type baseCompiler struct {
 	relative string
 	path     android.InstallPath
 	location installLocation
+	sanitize *sanitize
 
 	coverageOutputZipFile android.OptionalPath
 	distFile              android.OptionalPath