Merge pull request #73 from sourceryinstitute/update-readme

doc(README): add build/test info for CCE & NAG

Author: rouson

README.md

@@ -74,18 +74,52 @@ See [fpm manifest](./fpm.toml) for the dependencies and developer dependencies,
 that [fpm] automatically downloads and builds via the `fpm` command provided in
 the "[Downloding, Building, and Testing]" section below.
 
+Downloding
+----------
+```zsh
+git clone [email protected]:sourceryinstitute/sourcery
+```
 
-Downloding, Building, and Testing
----------------------------------
+Building and Testing
+--------------------
+### Single-image (serial) testing with GNU Fortran (`gfortran`) 
 With recent versions of [GNU Fortran] (gfortran) and [OpenCoarrays] installed, 
 execute the following command in a `zsh` or `bash`-like shell:
+```zsh
+fpm test
+```
 
+### Multi-image (parallel) testing with `gfortran` and OpenCoarrays
+With recent versions of [GNU Fortran] (gfortran) and [OpenCoarrays] installed, 
+execute the following command in a `zsh` or `bash`-like shell:
 ```zsh
-git clone [email protected]:sourceryinstitute/sourcery
 fpm test --compiler caf --runner "cafrun -n 4"
-  
 ```
-substituting the number of desired images for the "4" above.
+Substitute the desired number of images for the `4` above.
+
+### Testing with the Numerical Algorithms Group (`nagfor`) compiler
+```zsh
+fpm test --compiler nagfor --flag "-fpp -coarray=cosmp"
+```
+
+### Building and testing with the Cray Compiler Environment (CCE)
+Because `fpm` uses the compiler name to determine the compiler identity and because
+CCE provides one compiler wrapper, `ftn`, for invoking all compilers, you will
+need to invoke `ftn` in a shell script named to identify CCE compiler. For example,
+place a script named `crayftn.sh` in your path with the following contents and with
+executable privileges set appropriately:
+```
+#!/bin/bash
+
+ftn $@
+```
+Then build and test Sourcery with the command
+```
+fpm test --compiler crayftn.sh
+```
+
+### Building and testing with other compilers
+To use Sourcery with other compilers, please submit an issue or pull request. 
 
 Building the documentation
 --------------------------