[skip appveyor] compiler change according to recommendation and use gcc
also on macos which will further enable openmp (which is OK even for MPI
builds)
python:
- 3.6
- 3.7
-c_compiler: # [linux]
- - gcc # [linux]
-cxx_compiler: # [linux]
- - gxx # [linux]
+channel_sources:
+ - conda-forge/label/gcc7,defaults # [unix]
+ - conda-forge,defaults # [not unix]
+channel_targets:
+ - conda-forge gcc7 # [unix]
+ - conda-forge main # [not unix]
+c_compiler: # [unix]
+ - gcc # [unix]
+cxx_compiler: # [unix]
+ - gxx # [unix]
