Move pipeline variables into template

We need to include top-level variable groups but can only do so if we
use -name/value syntax.  Hide this in a template so that it's less ugly.

Author: ericstj

build/vsts-ci.yml

@@ -13,14 +13,7 @@ resources:
   - container: UbuntuCrossArm64Container
     image: mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-mlnet-cross-arm64
 variables:
-- group: SDL_Settings
-  BuildConfig: Release
-  OfficialBuildId: $(BUILD.BUILDNUMBER)
-  DOTNET_CLI_TELEMETRY_OPTOUT: 1
-  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: 1
-  DOTNET_MULTILEVEL_LOOKUP: 0
-  Codeql.Enabled: true
-  Codeql.SkipTaskAutoInjection: True  #default to not inject CodeQL tasks, we'll enable it in a single job.
+- template: /eng/common-variables.yml
 
 stages:
 - stage: build

eng/common-variables.yml

@@ -0,0 +1,17 @@
+variables:
+- group: SDL_Settings
+- name: BuildConfig
+  value: Release
+- name: OfficialBuildId
+  value: $(BUILD.BUILDNUMBER)
+- name: DOTNET_CLI_TELEMETRY_OPTOUT
+  value: 1
+- name: DOTNET_SKIP_FIRST_TIME_EXPERIENCE
+  value: 1
+- name: DOTNET_MULTILEVEL_LOOKUP
+  value: 0
+- name: Codeql.Enabled
+  value: true
+- name: Codeql.SkipTaskAutoInjection
+  value: True  #default to not inject CodeQL tasks, we'll enable it in a single job.
+