Make sure to actually use the toolchain specified

Author: Xanewok

ci/azure-install-rust.yml

@@ -4,6 +4,7 @@ steps:
       set -e
       curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain $RUSTUP_TOOLCHAIN
       echo "##vso[task.setvariable variable=PATH;]$PATH:$HOME/.cargo/bin"
+      $HOME/.cargo/bin/rustup default $RUSTUP_TOOLCHAIN
     env:
       RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
     displayName: "Install rust (*nix)"
@@ -16,6 +17,7 @@ steps:
       rustup-init.exe -y --default-toolchain %RUSTUP_TOOLCHAIN%
       set PATH=%PATH%;%USERPROFILE%\.cargo\bin
       echo "##vso[task.setvariable variable=PATH;]%PATH%;%USERPROFILE%\.cargo\bin"
+      %USERPROFILE%\.cargo\bin\rustup default %RUSTUP_TOOLCHAIN%
     env:
       RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
     displayName: Install rust (windows)