Merge changes from topic "update-prebuilts-r18b"

* changes:
  Don't use libandroid_support post-21.
  Up the NDK's minimum supported API level.
  Remove legacy NDK code.
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index d48ce58..d1d7c60 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -112,7 +112,6 @@
 	"mkdir":     Allowed,
 	"mktemp":    Allowed,
 	"mv":        Allowed,
-	"od":        Allowed,
 	"openssl":   Allowed,
 	"paste":     Allowed,
 	"patch":     Allowed,
@@ -138,7 +137,6 @@
 	"sort":      Allowed,
 	"stat":      Allowed,
 	"tar":       Allowed,
-	"tail":      Allowed,
 	"tee":       Allowed,
 	"timeout":   Allowed,
 	"todos":     Allowed,
@@ -173,7 +171,9 @@
 	"comm":   Toybox,
 	"env":    Toybox,
 	"id":     Toybox,
+	"od":     Toybox,
 	"sleep":  Toybox,
+	"tail":   Toybox,
 	"true":   Toybox,
 	"uname":  Toybox,
 	"uniq":   Toybox,