Update azure-pipelines.yml

.azure/azure-pipelines.yml

@@ -5,8 +5,6 @@ strategy:
   matrix:
     linux-nightly:
       image: ubuntu-16.04
-        commands:
-          - sudo apt-get -y install libxcb-composite0-dev libx11-dev
     macos-nightly:
       image: macos-10.14
     windows-nightly:
@@ -18,6 +16,10 @@ pool:
 steps:
   - bash: |
       set -e
+      if [ -e /etc/debian_version ]
+      then
+        sudo apt-get -y install libxcb-composite0-dev libx11-dev
+      fi
       curl https://sh.rustup.rs -sSf | sh -s -- -y --no-modify-path --default-toolchain `cat rust-toolchain`
       export PATH=$HOME/.cargo/bin:$PATH
       rustc -Vv