combine bootstrap for all OS

Author: aminya

script/vsts/platforms/linux.yml

@@ -16,7 +16,7 @@ jobs:
         parameters:
           OS: linux
 
-      - template: templates/linux-bootstrap.yml
+      - template: templates/bootstrap.yml
 
       - script: script/lint
         displayName: Run linter

script/vsts/platforms/macos.yml

@@ -18,7 +18,7 @@ jobs:
         parameters:
           OS: macos
 
-      - template: templates/macos-bootstrap.yml
+      - template: templates/bootstrap.yml
 
       - script: script/lint
         displayName: Run linter
@@ -70,6 +70,6 @@ jobs:
 
       # The artifact caching task does not work on forks, so we need to
       # bootstrap again for pull requests coming from forked repositories.
-      - template: templates/macos-bootstrap.yml
+      - template: templates/bootstrap.yml
 
       - template: templates/macos-test.yml

script/vsts/platforms/templates/bootstrap.yml

@@ -0,0 +1,20 @@
+steps:
+  - bash: $BootstrapScript
+    displayName: Bootstrap build environment
+    env:
+      CI: true
+      CI_PROVIDER: VSTS
+      ${{ if in(variables['Agent.OS'], 'Windows_NT') }}:
+        BootstrapScript: "node script\\vsts\\windows-run.js script\\bootstrap.cmd"
+        NPM_BIN_PATH: "C:\\hostedtoolcache\\windows\\node\\12.13.1\\x64\\npm.cmd"
+        BUILD_ARCH: $(buildArch)
+      ${{ if in(variables['Agent.OS'], 'Darwin', 'Linux') }}:
+        BootstrapScript: script/bootstrap
+        NPM_BIN_PATH: /usr/local/bin/npm
+      ${{ if in(variables['Agent.OS'], 'Darwin', 'Windows_NT') }}:
+        npm_config_build_from_source: true
+      ${{ if in(variables['Agent.OS'], 'Linux') }}:
+        CC: clang-5.0
+        CXX: clang++-5.0
+        npm_config_clang: 1
+      condition: or(ne(variables['MainNodeModulesRestored'], 'true'), ne(variables['ScriptNodeModulesRestored'], 'true'), ne(variables['ApmNodeModulesRestored'], 'true'))

script/vsts/platforms/templates/linux-bootstrap.yml

@@ -26,7 +26,7 @@ jobs:
         parameters:
           OS: windows
 
-      - template: templates/windows-bootstrap.yml
+      - template: templates/bootstrap.yml
 
       - script: node script\vsts\windows-run.js script\lint.cmd
         env: