Build binaries with older glibc Centos 6
Brent;
Is it possible to provide the pre-build binaries on Centos 6 with an older glibc? When using the current binaries on older systems I get:
```
mosdepth: /lib64/libc.so.6: version `GLIBC_2.14' not found (required by mosdepth)
```
It works fine on more up to date machines but we support these older ones with bioconda (and many bcbio HPC users have them).