pkg/vcs: use garnet instead of topaz layer for fuchsia

Topaz contains end user applications that are not interesting for us
and only increase build time. The applications also consume lots of memory,
so switching to garnet should leave more memory for the fuzzer
(maybe eliminate some OOMs).

pkg/vcs/fuchsia.go

@@ -52,7 +52,7 @@ func (ctx *fuchsia) initRepo() error {
 		return err
 	}
 	cmd := "curl -s 'https://fuchsia.googlesource.com/scripts/+/master/bootstrap?format=TEXT' |" +
-		"base64 --decode | bash -s topaz"
+		"base64 --decode | bash -s garnet"
 	if _, err := runSandboxed(tmpDir, "bash", "-c", cmd); err != nil {
 		return err
 	}