Reconfig on compiler version change

[chrispbradley]

The archpath contains the compiler major and minor version numbers so that changes in object file formats can be kept isolated from older versions etc. The trouble is when the compiler is upgraded. You can go into the build directories and issue make and it has to done a reconfig it will start to use the wrong directory. There should be a check at the start of make that the version number of the compiler is the same as the configured version and issue a warning to reconfigure all if there is a change.