@ahmadia --- how could you use the "when" class? It seems that there is no "else" keyword, so I don't know how that could be done. I need something like:
```
extends: [cmake_package]

sources:
- url: http://www.netlib.org/lapack/lapack-3.4.2.tgz
  key: tar.gz:mctf3kxrn3brka2gowkcmgfcemcsd2t2

build_stages:
- name: configure
  build_in_source: true
  when compiler == 'gcc':
      extra: ['-D CMAKE_BUILD_TYPE:STRING=Release',
              '-D CMAKE_Fortran_FLAGS_RELEASE:STRING="-O3 -fPIC -march=native -ffast-math -funroll-loops"',
              '-D CMAKE_INSTALL_RPATH:STRING="${ARTIFACT}/lib"',
              '-D CMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOL=ON',
              '-D BUILD_TESTING:BOOL=OFF',
              '-D BUILD_SHARED_LIBS:BOOL=ON',
              ]
  else:
      extra: ['-D CMAKE_BUILD_TYPE:STRING=Release',
              '-D CMAKE_INSTALL_RPATH:STRING="${ARTIFACT}/lib"',
              '-D CMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOL=ON',
              '-D BUILD_TESTING:BOOL=OFF',
              '-D BUILD_SHARED_LIBS:BOOL=ON',
              ]

- name: setup_builddir
  mode: override
  bash: |
```

Even better would be to somehow just append the extra line that is needed for gcc at the end of the list. Any ideas how to do this kind of thing?