Can't launch AVD on macOS 10.13
Solution 1:
Use the new Hypervisor.Framework support instead of HAXM on macOS, as described in the comments of the issue filed for this:
Try running the emulator on Canary channel 26.1.x (API 25/26 recommended) with Hypervisor.Framework; put the text "HVF = on" in ~/.android/advancedFeatures.ini (create this file if it doesn't exist already).
Solution 2:
You can download and install the latest version haxm https://github.com/intel/haxm/releases/latest