[Bug libgomp/84020] New: [nvptx] Add GOMP_NVPTX_JIT=-O[0-4] in nvptx libgomp plugin

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84020

            Bug ID: 84020
           Summary: [nvptx] Add GOMP_NVPTX_JIT=-O[0-4] in nvptx libgomp
                    plugin
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: libgomp
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---

patch submitted at https://gcc.gnu.org/ml/gcc-patches/2018-01/msg02004.html and
approved for gcc 9 stage 1, and approved here:
https://gcc.gnu.org/ml/gcc-patches/2018-01/msg02005.html .

Filing this PR to remember to commit in stage1.