Spack-stack 1.7.0 failing with Intel 2018.4 on Orion

**Describe the bug**
Spack-stack 1.7.0 failing with Intel 2018.4 on Orion

**To Reproduce**
Install spack-stack 1.7.0 on Orion, Intel environment

**Expected behavior**
Fails with "internal compiler error"

**System:**
Orion

**Additional context**
Fixed by removing 2018.4 from compilers.yaml and package.yaml files.
