Fix integration tests

tracer/test/Datadog.Trace.ClrProfiler.IntegrationTests/InstrumentationTests.cs

@@ -137,9 +137,14 @@ public async Task InstrumentsDotNetTest()
         public async Task WhenUsingRelativeTracerHome_InstrumentsApp()
         {
             SetEnvironmentVariable("DD_INTERNAL_WAIT_FOR_DEBUGGER_ATTACH", "1");
-            var path = Path.GetRelativePath(EnvironmentHelper.GetSampleApplicationOutputDirectory(), EnvironmentHelper.MonitoringHome);
+            // the working dir when we run the app is the _test_ project, not the app itself, so we need to be relative to that
+            // This is a perfect example of why we don't recommend using relative paths for these variables
+            var workingDir = Environment.CurrentDirectory;
+            var monitoringHome = EnvironmentHelper.MonitoringHome;
+            var path = PathUtil.GetRelativePath(workingDir, monitoringHome);
+            var effectivePath = Path.GetFullPath(Path.Combine(workingDir, path));
+            Output.WriteLine($"Using DD_DOTNET_TRACER_HOME={path} with workingDir={workingDir} and monitoringHome={monitoringHome}, giving an effective path of {effectivePath}");
             SetEnvironmentVariable("DD_DOTNET_TRACER_HOME", path);
-            Output.WriteLine("Using DD_DOTNET_TRACER_HOME " + path);
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);
             using var processResult = await RunSampleAndWaitForExit(agent, "traces 1");
             agent.Spans.Should().NotBeEmpty();
@@ -152,7 +157,7 @@ public async Task WhenUsingPathWithDotsInInTracerHome_InstrumentsApp()
         {
             SetEnvironmentVariable("DD_INTERNAL_WAIT_FOR_DEBUGGER_ATTACH", "1");
             // not using Path.Combine here because it resolves the .. and we want it in the path
-            var path = EnvironmentHelper.MonitoringHome + "/../" + Path.GetFileName(EnvironmentHelper.MonitoringHome);
+            var path = Path.Combine(EnvironmentHelper.MonitoringHome, "..", Path.GetFileName(EnvironmentHelper.MonitoringHome)!);
             Output.WriteLine("Using DD_DOTNET_TRACER_HOME " + path);
             SetEnvironmentVariable("DD_DOTNET_TRACER_HOME", path);
             using var agent = EnvironmentHelper.GetMockAgent(useTelemetry: true);