Switch to toybox xargs(1).

Test: treehugger
Change-Id: I8db68577498c1f6c0e1fdff951bc8972184b2754
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index fdd291e..1afcf55 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -123,7 +123,6 @@
 	"unzip":     Allowed,
 	"wc":        Allowed,
 	"which":     Allowed,
-	"xargs":     Allowed,
 	"xz":        Allowed,
 	"zip":       Allowed,
 	"zipinfo":   Allowed,
@@ -176,6 +175,7 @@
 	"uniq":     Toybox,
 	"unix2dos": Toybox,
 	"whoami":   Toybox,
+	"xargs":    Toybox,
 	"xxd":      Toybox,
 }