use yarn --frozen-lockfile for builds

build/azure-pipelines/darwin/continuous-build-darwin.yml

@@ -11,7 +11,7 @@ steps:
   inputs:
     versionSpec: "1.10.1"
 - script: |
-    yarn
+    yarn --frozen-lockfile
   displayName: Install Dependencies
   condition: ne(variables['CacheRestored'], 'true')
 - task: 1ESLighthouseEng.PipelineArtifactCaching.SaveCacheV1.SaveCache@1

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

@@ -37,7 +37,7 @@ steps:
 
 - script: |
     set -e
-    yarn
+    yarn --frozen-lockfile
   displayName: Install dependencies
 
 - script: |

build/azure-pipelines/linux/continuous-build-linux.yml

@@ -19,7 +19,7 @@ steps:
   inputs:
     versionSpec: "1.10.1"
 - script: |
-    yarn
+    yarn --frozen-lockfile
   displayName: Install Dependencies
   condition: ne(variables['CacheRestored'], 'true')
 - task: 1ESLighthouseEng.PipelineArtifactCaching.SaveCacheV1.SaveCache@1

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

@@ -46,7 +46,7 @@ steps:
 
 - script: |
     set -e
-    CHILD_CONCURRENCY=1 yarn
+    CHILD_CONCURRENCY=1 yarn --frozen-lockfile
   displayName: Install dependencies
 
 - script: |

build/azure-pipelines/linux/product-build-linux-arm.yml

@@ -46,7 +46,7 @@ steps:
 
 - script: |
     set -e
-    CHILD_CONCURRENCY=1 yarn
+    CHILD_CONCURRENCY=1 yarn --frozen-lockfile
   displayName: Install dependencies
 
 - script: |

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

@@ -38,7 +38,7 @@ steps:
 
 - script: |
     set -e
-    CHILD_CONCURRENCY=1 yarn
+    CHILD_CONCURRENCY=1 yarn --frozen-lockfile
   displayName: Install dependencies
 
 - script: |

build/azure-pipelines/win32/continuous-build-win32.yml

@@ -15,7 +15,7 @@ steps:
     targetfolder: '**/node_modules, !**/node_modules/**/node_modules'
     vstsFeed: '$(ArtifactFeed)'
 - powershell: |
-    yarn
+    yarn --frozen-lockfile
   displayName: Install Dependencies
   condition: ne(variables['CacheRestored'], 'true')
 - task: 1ESLighthouseEng.PipelineArtifactCaching.SaveCacheV1.SaveCache@1

build/azure-pipelines/win32/product-build-win32.yml

@@ -40,7 +40,7 @@ steps:
     $ErrorActionPreference = "Stop"
     $env:npm_config_arch="$(VSCODE_ARCH)"
     $env:CHILD_CONCURRENCY="1"
-    exec { yarn }
+    exec { yarn --frozen-lockfile }
   displayName: Install dependencies
 
 - powershell: |

build/npm/postinstall.js

@@ -20,13 +20,10 @@ function yarnInstall(location, opts) {
 	const raw = process.env['npm_config_argv'] || '{}';
 	const argv = JSON.parse(raw);
 	const original = argv.original || [];
-	const args = ['install'];
+	const args = original.filter(arg => arg === '--ignore-optional' || arg === '--frozen-lockfile');
 
-	if (original.indexOf('--ignore-optional') > -1) {
-		args.push('--ignore-optional');
-	}
-
-	console.log('Installing dependencies in \'%s\'.', location);
+	console.log(`Installing dependencies in ${location}...`);
+	console.log(`$ yarn ${args.join(' ')}`);
 	const result = cp.spawnSync(yarn, args, opts);
 
 	if (result.error || result.status !== 0) {