[Chapel Merge] Upgrade XC-x86 gcc gen compiler to 8.3.0

Branch: refs/heads/master
Revision: c7d6f23
Author: ronawho
Log Message:

Merge pull request #16407 from ronawho/upgrade-gen-compiler

Upgrade XC-x86 gcc gen compiler to 8.3.0

Modified Files:
M util/build_configs/cray-internal/setenv-xc-x86_64.bash

Compare: https://github.com/chapel-lang/chapel/compare/745dfa2e64b4...c7d6f2333818