rust: collect file dependencies for clippy

Previously, the clippy rule did not keep track of the source files for
which a modification would require the target to be rebuilt. Similarly
to the rustc rule, ensure that we capture all the dependencies via the
dep-info output.

Bug: 181298002
Test: m libkeystore2; inspect generated .clippy.d
Change-Id: Icfc7074e1fca38f7782544e6c436ffbfc6c9b4e0

rust/builder.go

@@ -51,9 +51,12 @@ var (
 			Command: "$envVars $clippyCmd " +
 				// Because clippy-driver uses rustc as backend, we need to have some output even during the linting.
 				// Use the metadata output as it has the smallest footprint.
-				"--emit metadata -o $out $in ${libFlags} " +
-				"$rustcFlags $clippyFlags",
+				"--emit metadata -o $out --emit dep-info=$out.d.raw $in ${libFlags} " +
+				"$rustcFlags $clippyFlags" +
+				" && grep \"^$out:\" $out.d.raw > $out.d",
 			CommandDeps: []string{"$clippyCmd"},
+			Deps:        blueprint.DepsGCC,
+			Depfile:     "$out.d",
 		},
 		"rustcFlags", "libFlags", "clippyFlags", "envVars")