Update min-platform-tools from 16 to 18.

Change-Id: Ie9eecf03932690df2b42423449333cc22835c82a
(cherry picked from commit 07b70764b0708159951222f9449629136c9f01b9)
diff --git a/files/tools_source.properties b/files/tools_source.properties
index 4e57c28..1f2e321 100644
--- a/files/tools_source.properties
+++ b/files/tools_source.properties
@@ -1,3 +1,3 @@
 Pkg.UserSrc=false
 Pkg.Revision=22.2.0
-Platform.MinPlatformToolsRev=16
+Platform.MinPlatformToolsRev=18