Add build notes to README

README.md

@@ -12,15 +12,19 @@ Please test this firmware and let us know if it misbehaves in any way. Volunteer
 
 __Not for production use. Use with caution!__
 
-Marlin 2.0 is bringing open source RepRap firmware to the next level with support of much faster 32-bit processor boards.
+Marlin 2.0 takes this popular RepRap firmware to the next level with support for much faster 32-bit processor boards.
 
 This branch is for patches to the latest 2.0.x release version. Periodically this branch will form the basis for the next minor 2.0.x release.
 
 Download earlier versions of Marlin on the [Releases page](https://github.com/MarlinFirmware/Marlin/releases).
 
+## Building Marlin 2.0
+
+To build Marlin 2.0 you'll need [Arduino IDE 1.9](https://www.arduino.cc/en/main/software) or [PlatformIO](http://docs.platformio.org/en/latest/ide.html#platformio-ide). We've posted detailed instructions on how to [build Marlin 2.0 for ARM](http://marlinfw.org/docs/basics/install_arm.html).
+
 ## Hardware Abstraction Layer (HAL)
 
-Marlin 2.0 adds a new abstraction layer so that Marlin can build and run on 32-bit boards while still retaining the ability to build and run on 8-bit AVR. In this way, new features can be enhanced for more powerful platforms while still supporting AVR, whereas splitting up the code makes it hard to follow these changes and keep them in sync.
+Marlin 2.0 adds a new abstraction layer so that Marlin can build and run on 32-bit boards while still retaining full 8-bit AVR compatibility. In this way, features can be enhanced for more powerful platforms while still supporting AVR, whereas splitting up the code would make it harder to maintain and keep everything in sync.
 
 ### Current HALs