I can not install any brew packages on my mac with the following error info.
Installed on my Mac:
You will need to install both "Xcode 10.0 Beta" from https://developer.apple.com/download/ AND "Command Line Tools (macOS 10.14) for Xcode 10 Beta" from
https://download.developer.apple.com/Developer_Tools/Command_Line_Tools_macOS_10.14_for_Xcode_10/Command_Line_Tools_macOS_10.14_for_Xcode_10.dmg
Update contributed by other comments, after you installed "Command Line Tools", you will also need to execute the following command in your terminal.
open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg