I haven’t done anything with Daydream. But I’ve done a lot of stuff with Gear VR and built successfully for Android on macOS. To build for Android on macOS, AndroidWorks should be installed. It’s in the Engine install directory (in 4.15-binary its under Engine–>Extras–>AndroidWorks–>Mac–>CodeWorksforAndroid-1R5-osx.dmg).
I’m actually building off of the Tegra Android Developer Pack (TADP), but support for that was discontinued by Nvidia, so Epic now uses AndroidWorks.
If the core issue is not being able to build for Android, you should start a new Question about it.