Merge pull request YosysHQ#123 from gojimmypi/patch-1

include example ECP5 architecture syntax

README.md

@@ -30,8 +30,8 @@ Out-of-tree builds are currently unsupported when coupled with `nextpnr`:
 
 Clone and install **latest git master** versions (Yosys 0.8 is not sufficient for ECP5 development) of [Yosys](https://github.com/YosysHQ/yosys)
  and [nextpnr](https://github.com/YosysHQ/nextpnr) according to their own instructions. Ensure
- to include the ECP5 architecture when building nextpnr; and point it towards your prjtrellis
- folder.
+ to include the [ECP5 architecture](https://github.com/YosysHQ/nextpnr#nextpnr-ecp5) when building nextpnr; and point it towards your prjtrellis
+ folder.  (for example: `cmake -DARCH=ecp5 -DTRELLIS_INSTALL_PREFIX=/usr/share/trellis/ .`)
 
 You should now be able to build the [examples](examples).