Pray bash works

ci/azure-install-rust.yml

@@ -15,20 +15,21 @@ steps:
     displayName: Install rust (unix)
     condition: ne( variables['Agent.OS'], 'Windows_NT' )
 
-  - powershell: |
-      if (!$env:TOOLCHAIN) {
-        $env:TOOLCHAIN = "stable-${env:TARGET}";
-      }
-      if ($env:RUSTUP_HOME) {
-        rustup update --no-self-update $env:TOOLCHAIN
-        rustup default $env:TOOLCHAIN
-      } else {
+  - bash: |
+      set -e
+      toolchain=$TOOLCHAIN
+      if [ "$toolchain" = "" ]; then
+        toolchain=stable-$TARGET
+      fi
+      if command -v rustup; then
+        rustup update $toolchain
+        rustup default $toolchain
+      else
         curl.exe -sSf -o rustup-init.exe https://win.rustup.rs
         ./rustup-init.exe -y --default-toolchain $env:TOOLCHAIN
-        Write-Host "##vso[task.prependpath]${env:USERPROFILE}/.cargo/bin"
-      }
+        echo "##vso[task.prependpath]$USERPROFILE/.cargo/bin"
+      fi
     displayName: Install rust (windows)
-    failOnStderr: false
     condition: eq( variables['Agent.OS'], 'Windows_NT' )
 
   - script: |