Skip platform tests in CI

src/BizHawk.Tests/BizHawk.Tests.csproj

@@ -5,6 +5,7 @@
 	</PropertyGroup>
 	<Import Project="../MainSlnCommon.props" />
 	<PropertyGroup>
+		<DefineConstants Condition=" '$(GITLAB_CI)' != '' Or '$(APPVEYOR)' != '' ">$(DefineConstants);SKIP_PLATFORM_TESTS</DefineConstants>
 		<OutputPath>$(ProjectDir)../../test_output</OutputPath>
 	</PropertyGroup>
 	<ItemGroup>

src/BizHawk.Tests/PlatformTests/Common.PathExtensions/PathExtensionTests.cs

@@ -13,6 +13,8 @@ namespace BizHawk.Tests.Common.PathExtensions
 		[TestMethod]
 		public void TestNullability()
 		{
+			PlatformTestUtils.RunEverywhere();
+
 			var p = OSTailoredCode.IsUnixHost ? "/" : @"C:\";
 
 			Assert.IsFalse(PE.IsSubfolderOf(childPath: null, parentPath: p));

src/BizHawk.Tests/PlatformTests/PlatformTestUtils.cs

@@ -8,17 +8,36 @@ namespace BizHawk.Tests
 	{
 		public static void OnlyRunOnRealUnix()
 		{
+#if SKIP_PLATFORM_TESTS
+			Assert.Inconclusive();
+#else
 			if (!OSTailoredCode.IsUnixHost || OSTailoredCode.IsWSL) Assert.Inconclusive();
+#endif
 		}
 
 		public static void OnlyRunOnUnix()
 		{
+#if SKIP_PLATFORM_TESTS
+			Assert.Inconclusive();
+#else
 			if (!OSTailoredCode.IsUnixHost) Assert.Inconclusive();
+#endif
 		}
 
 		public static void OnlyRunOnWindows()
 		{
+#if SKIP_PLATFORM_TESTS
+			Assert.Inconclusive();
+#else
 			if (OSTailoredCode.IsUnixHost) Assert.Inconclusive();
+#endif
+		}
+
+		public static void RunEverywhere()
+		{
+#if SKIP_PLATFORM_TESTS
+			Assert.Inconclusive();
+#endif
 		}
 	}
 }