fx3_firmware: Updated README.md

Updated README to reflect that The build now requires a kludgy
combination of CMake and toolchain.mk.

This (Isssue #174) is still on the radar to clean up.

fx3_firmware/README.md

@@ -22,8 +22,10 @@ Once the SDK is downloaded, building the firmware requires a file defining the t
 
 1. Create your own `toolchain.mk` file from the example given: `cp make/toolchain.mk.sample make/toolchain.mk`
 2. Modify your `make/toolchain.mk` to declare an `FX3_ROOT` where the SDK was installed.
-3. Compile the firmware using `make`.  Use `DEBUG=yes` if you want to include debug symbols.
-4. The file `bladeRF.img` should have been produced with a note saying that 256 bytes of interrupt vector code have been removed.  This warning is normal and you have just built the FX3 firmware successfully!
+3. Create and enter a `build/` directory
+4. Run `cmake ../`
+5. Compile the firmware vi `make`.
+6. The file `bladeRF.img` should have been produced with a note saying that 256 bytes of interrupt vector code have been removed.  This warning is normal and you have just built the FX3 firmware successfully!
 
 ### Eclipse ###
 The FX3 SDK provides an Eclipse-based IDE. A project file for this tool is provided in this directory. To import this project, perform the following steps.