Using build-time sysroot breaks the conda package on OS X

[SylvainCorlay]

In our conda packaging for v0.6, we had to revert the change introduced in commit https://github.com/root-project/cling/commit/c23abbc88b6ee61b966291c785794743b1bd5c62 which switches from detecting the sysroot at runtime from using the build time value.

The problem is that we cannot distribute the OS X SDK in a conda package because of license reasons. Hence, we build things with an old version of the SDK (0.10.9) so that it can run with newer ones.

However, with that change, cling will look exactly at where the SDK was at build time, which prevents distributing a binary of cling on a different machine like we do with conda.

cc @chrisburr

[chrisburr]

@SylvainCorlay Glad to see cling now seems to be working!

To add, for the ROOT package on conda-forge this revert is also been needed and is provided by this patch: root-x.xx.xx_cling-runtime-sysroot.patch

EDIT: I've mixed up sysroot patches. The commit mentioned is actually reverted by us indirectly using this patch: root-x.xx.xx-osx-remove-hardcoded-sysroot.patch