The 6.0-rc2 release is based on the latest Android Marshmallow-MR2 release (6.0.1_r61) with all AOSP security patches applied. We fixed a lot of issues found in the since 6.0-rc1 and added more features:
We create universal images for most x86 platforms. This release contains two files. One is the 32-bit x86 ISO and the other is the 64-bit x86_64 ISO. Both can be boot from legacy BIOS and newer UEFI firmware. You can choose one of them depends on your devices. In doubt, try the 32-bit ISO for legacy BIOS devices and 64-bit ISO for UEFI devices.
Both files can be dumped into a usb drive to create a bootable usb stick like :
dd if=android-x86-6.0-rc2.iso of=/dev/sdX
where /dev/sdX is the device name of your usb drive.
Windows's users can use the tool Win32 Disk Imager to create a bootable usb stick.
Please read this page about how to install it to the device.
repo init -u git://git.osdn.net/gitroot/android-x86/manifest -b marshmallow-x86
Read this page for how to compile source code.