ci: install qemu for alpine arm64 (microsoft#188455)

Author: deepak1556

build/azure-pipelines/alpine/product-build-alpine.yml

@@ -78,6 +78,7 @@ steps:
         echo "Yarn failed $i, trying again..."
       done
     env:
+      npm_config_arch: $(NPM_ARCH)
       ELECTRON_SKIP_BINARY_DOWNLOAD: 1
       PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD: 1
       GITHUB_TOKEN: "$(github-distro-mixin-password)"

build/azure-pipelines/product-build.yml

@@ -481,6 +481,7 @@ stages:
           - job: LinuxAlpine
             variables:
               VSCODE_ARCH: x64
+              NPM_ARCH: x64
             steps:
               - template: alpine/product-build-alpine.yml
 
@@ -489,6 +490,7 @@ stages:
             timeoutInMinutes: 120
             variables:
               VSCODE_ARCH: arm64
+              NPM_ARCH: arm64
             steps:
               - template: alpine/product-build-alpine.yml