Properly set working directory when running post install hooks

src/Squirrel/UpdateManager.ApplyReleases.cs

@@ -408,7 +408,7 @@ namespace Squirrel
                         cts.CancelAfter(15 * 1000);
 
                         try {
-                            await Utility.InvokeProcessAsync(exe, args, cts.Token).ConfigureAwait(false);
+                            await Utility.InvokeProcessAsync(exe, args, cts.Token, Path.GetDirectoryName(exe)).ConfigureAwait(false);
                         } catch (Exception ex) {
                             this.Log().ErrorException("Couldn't run Squirrel hook, continuing: " + exe, ex);
                         }

test/ApplyReleasesTests.cs

@@ -90,7 +90,8 @@ namespace Squirrel.Tests
                 Assert.True(File.Exists(Path.Combine(tempDir, "theApp", "app-0.2.0", "args.txt")));
 
                 var text = File.ReadAllText(Path.Combine(tempDir, "theApp", "app-0.2.0", "args.txt"), Encoding.UTF8);
-                Assert.Contains("updated|0.2.0", text);
+                Assert.Contains("updated", text);
+                Assert.Contains("0.2.0", text);
             }
         }