fix cmd syntax

Author: gcampbell-msft

build/build.yml

@@ -54,12 +54,12 @@ jobs:
     condition: and(succeeded(), startsWith(variables['Build.SourceBranch'], 'refs/tags'))
   - ${{ if parameters.prerelease }}:
     - script: |
-        $env:NODE_OPTIONS="--openssl-legacy-provider --no-experimental-fetch"
+        set NODE_OPTIONS="--openssl-legacy-provider --no-experimental-fetch"
         node build/package.js --pre-release
       displayName: Build and pack extension
   - ${{ else }}:
     - script: |
-        $env:NODE_OPTIONS="--openssl-legacy-provider --no-experimental-fetch"
+        set NODE_OPTIONS="--openssl-legacy-provider --no-experimental-fetch"
         node build/package.js
       displayName: Build and pack extension
   - pwsh: |