I guess this is a bug or feature request:
Installing Antergos in a multiboot system and not selecting the bootloader install option, because I am using my own bootloader/partition, resulted in a non-bootable system.
Scenario: MBR system and installing Antergos into single logical partition /dev/sda7.
The installer marked the /dev/sda7 as active/bootable, which is invalid, resulting in the system being unable to boot, until I went in with rescue disk and restored boot flag to the primary partition that had the boot flag prior to install.
Again, I don’t need help with this and have repaired the system, just reporting what I encountered during install.