Use toybox md5sum instead of md5 on macOS.

Test: builds locally
Change-Id: I04aa52de96e0525a44331cb0c057a8e18a95891d
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index b97391b..786e7d3 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -129,12 +129,10 @@
 
 func init() {
 	if runtime.GOOS == "darwin" {
-		// TODO: move Darwin off md5 and onto our md5sum prebuilt.
-		Configuration["md5"] = Allowed
 		Configuration["sw_vers"] = Allowed
 		Configuration["xcrun"] = Allowed
 
-		// We don't have darwin prebuilts for some tools (like toybox),
+		// We don't have darwin prebuilts for some tools,
 		// so allow the host versions.
 		for name, config := range Configuration {
 			if config.LinuxOnlyPrebuilt {