Refer to mosdepth correctly like other tools

[hdashnow]

Set mosdepth in pipeline_config (via install script) rather than referring to it in pipeline_stages as $STRETCH/tools/bin/mosdepth

[wykswr]

I guess there is a bug in ./STRetch_exome_bam_pipeline.groovy with $STRETCH/tools/bin/mosdepth but not $mosdepth, making it crash when dealing with cram inputs.

[hdashnow]

You're seeing a specific version of mosdepth crash on crams? Which version?