Conan env extracted from ci script.

.github/workflows/ci.yml

     steps:
       - uses: actions/checkout@master
       - name: Build
-        env:
-          CONAN_GCC_VERSIONS: 9
-        run: script/conan_build.sh
+        run: |
+          export CONAN_GCC_VERSIONS=9
+          export CONAN_DOCKER_IMAGE=conanio/gcc${CONAN_GCC_VERSIONS}
+          script/conan_build.sh

script/conan_build.sh

 
 set -ex
 
-export CONAN_DOCKER_IMAGE=conanio/gcc${CONAN_GCC_VERSIONS}
 export CONAN_ARCHS="x86_64"
 export CONAN_BUILD_TYPES=Release