DAR: Allow caller to control VSASSERT path (#1489)

For other internal clients, it would be helpful if one could control the VSASSERT path, as this path is also used to write out where dump files are stored on Windows. This PR updates support to enable this.

Author: gregg-miskelly

test/DebugAdapterRunner/DebugAdapterRunner.cs

@@ -8,6 +8,7 @@
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Threading;
 
@@ -163,8 +164,25 @@ private void StartDebugAdapter(
 
             if (redirectVSAssert)
             {
-                _assertionFileName = Path.Combine(Path.GetTempPath(), string.Format(CultureInfo.InvariantCulture, "vsassert.{0}.txt", Guid.NewGuid()));
-                startInfo.Environment["VSASSERT"] = _assertionFileName;
+                string vsassertPath = null;
+
+                // First see if the caller already specified the assertion path
+                if (additionalEnvironmentVariables != null)
+                {
+                    vsassertPath = additionalEnvironmentVariables
+                        .Where(pair => pair.Key.Equals("VSASSERT", StringComparison.OrdinalIgnoreCase))
+                        .Select(pair => pair.Value)
+                        .FirstOrDefault();
+                }
+
+                if (string.IsNullOrEmpty(vsassertPath))
+                {
+                    // If the caller didn't specify a path, create a temporary one
+                    vsassertPath = Path.Combine(Path.GetTempPath(), string.Format(CultureInfo.InvariantCulture, "vsassert.{0}.txt", Guid.NewGuid()));
+                    startInfo.Environment["VSASSERT"] = vsassertPath;
+                }
+
+                _assertionFileName = vsassertPath;
             }
 
             if (additionalEnvironmentVariables != null)