USE SIXLABORS_TESTING instead of CI Env var

.github/workflows/build-and-test.yml

@@ -79,12 +79,14 @@ jobs:
             - name: Build
               shell: pwsh
               run: ./ci-build.ps1 "${{matrix.options.framework}}"
+              env:
+                SIXLABORS_TESTING: True
 
             - name: Test
               shell: pwsh
               run: ./ci-test.ps1 "${{matrix.options.os}}" "${{matrix.options.framework}}" "${{matrix.options.runtime}}" "${{matrix.options.codecov}}"
               env:
-                  CI: True
+                  SIXLABORS_TESTING: True
                   XUNIT_PATH: .\tests\ImageSharp.Tests # Required for xunit
 
             - name: Export Failed Output

src/ImageSharp/ImageSharp.csproj

@@ -15,7 +15,7 @@
   </PropertyGroup>
 
   <Choose>
-    <When Condition="$(CI) == true">
+    <When Condition="$(SIXLABORS_TESTING) == true">
       <PropertyGroup>
         <TargetFrameworks>net5.0;netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
       </PropertyGroup>