[xharness] Only run xammac variations if macOS tests are included. (#…

…9729)

This fixes a build error with a xammac test variation that is executed even if
the macOS build is disabled.

tests/xharness/Jenkins/TestVariationsFactory.cs

@@ -123,7 +123,7 @@ IEnumerable<TestData> GetTestData (RunTestTask test)
 						yield return new TestData { Variation = "Release (all optimizations)", MonoBundlingExtraArgs = "--registrar:static --optimize:all", Debug = false, LinkMode = "Full", Defines = "OPTIMIZEALL"};
 						break;
 					case "Debug":
-						yield return new TestData { Variation = "Debug (all optimizations)", MonoBundlingExtraArgs = "--registrar:static --optimize:all,-remove-uithread-checks", Debug = true, LinkMode = "Full", Defines = "OPTIMIZEALL", Ignored = !jenkins.IncludeAll };
+						yield return new TestData { Variation = "Debug (all optimizations)", MonoBundlingExtraArgs = "--registrar:static --optimize:all,-remove-uithread-checks", Debug = true, LinkMode = "Full", Defines = "OPTIMIZEALL", Ignored = !(jenkins.IncludeAll && jenkins.IncludeMac) };
 						break;
 					}
 					break;