update buildscript.sh for AppleClang

[Steven Hahn]

update the buildscript so that it works with clang in the pull request matrix.

[Steven Hahn]

Refs #11136. Change how clang build is determined

Changeset: 979fd658b19d44a9cc98230f210f1f919feba238

[Steven Hahn]

This is being verified as ​pull request #255.

[Pete Peterson]

Re #11136. Reworked if/else logic

Changeset: bc84bb9fdd03816f1608b8322386c0cbe265a075

[Martyn Gigg]

I think the script looks fine. Despite the green tick though, if you look at the build log for [10.8](​http://builds.mantidproject.org/job/pull_requests/640/label=osx-10.8-build/consoleFull) you'll see an error ` /Users/builder/jenkins-linode/workspace/pull_requests/label/osx-10.8-build/Code/Mantid/Build/Jenkins/buildscript: line 29: [[false: command not found `

It looks to me as if in the build of bc84bb9 it has actually built the previous merge. I'll retest it just to be sure.

[Martyn Gigg]

Jenkins, retest this please

[Martyn Gigg]

The build failure is on rhel6 and is a problem checking out the pull request. The ubuntu build has covered a Linux environment so I this we can :shipit:

[Martyn Gigg]

Merge pull request #255 from mantidproject/11136_update_buildscript_clang

Change how clang builds are determined

Full changeset: ​b6076970554a85db1d7191b46123d087812b04dd

[Nick Draper]

Somehow these slipped through without a resolution. Set to Fixed.

[Stuart Campbell]

This ticket has been transferred to github issue ​11975