hwloc's detect.sh fails if hwloc-info is not installed

[Roland Haas]

Git hash c1b1ec0 "hwloc: add workarounds to get hwloc version for pre 2.1 hwloc" of ExternalLibraries-hwloc introduced code into hwloc’s detect.sh that uses hwloc-info to find out the library version. This code causes detect.sh to fail if hwloc-info is not present.

This pull request

https://github.com/EinsteinToolkit/ExternalLibraries-hwloc/pull/new/rhaas/hwloc-location

adds checks about whether hwloc-info exists before using it.

[Roland Haas]

Please review.

[Roland Haas]

Applied as git hash c08af6f "hwloc: check if hwloc-info exists before using it" of ExternalLibraries-hwloc