[tests] Does monodroid-config.xml exist?

Context: #7081
Context: #7073 (comment)

Trying to figure out why the `InstallAndroidDependenciesTest()` is
failing.  My *guess* is that `monodroid-config.xml` exists, causing
the `$(_AndroidSdkPath)` output property to use a *system-wide*
installation path, instead of the desired `$(AndoridSdkDirectory)`
input value.

PR #7081 tested behavior against main, and determined that
`monodroid-config.xml` doesn't exist, which may be why this test
passes on main.

Update #7073 to also assert the (non-?)existence of
`monodroid-config.xml`.  If it *does* exist, this would explain why
it's failing.

*If* it's failing because of `monodroid-config.xml`, the next question
becomes *why* it exists.  Update `BaseTest.TestSetup()` to assert
that it doesn't exist; when it does exist, tests will begin failing.

Author: jonpryor

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/AndroidDependenciesTests.cs

@@ -40,13 +40,15 @@ public void InstallAndroidDependenciesTest ()
 						"AndroidManifestType=GoogleV2",     // Need GoogleV2 so we can install API-32
 					}), "InstallAndroidDependencies should have succeeded.");
 					b.Target = defaultTarget;
+					TestContext.Out.WriteLine ($"[TESTLOG] `{_configPath}` exists? {File.Exists (_configPath)}");
 					Assert.IsTrue (b.Build (proj, true), "build should have succeeded.");
 					Assert.IsTrue (b.LastBuildOutput.ContainsText ($"Output Property: _AndroidSdkDirectory={sdkPath}"), "_AndroidSdkDirectory was not set to new SDK path.");
 					Assert.IsTrue (b.LastBuildOutput.ContainsText ($"JavaPlatformJarPath={sdkPath}"), "JavaPlatformJarPath did not contain new SDK path.");
 				}
 			} finally {
 				Environment.SetEnvironmentVariable ("ANDROID_SDK_PATH", old);
 			}
+			throw new Exception ($"# jonp: deliberate test failure! File.Exist(\"{_configPath}\")? {File.Exists (_configPath)}");
 		}
 
 		[Test]

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Utilities/BaseTest.cs

@@ -630,11 +630,17 @@ protected void AssertExtractNativeLibs (string manifest, bool extractNativeLibs)
 			}
 		}
 
+		protected static string _configPath = Path.Combine (Environment.GetFolderPath (Environment.SpecialFolder.ApplicationData), "xbuild", "monodroid-config.xml");
+
 		[SetUp]
 		public void TestSetup ()
 		{
 			TestContext.Out.WriteLine ($"[TESTLOG] Test {TestName} Starting");
 			TestContext.Out.Flush ();
+			if (System.IO.File.Exists (_configPath)) {
+				TestContext.Out.WriteLine ($"[TESTLOG] `{_configPath}` exists!");
+				throw new Exception ($"# jonp: deliberate test failure! File.Exist(\"{_configPath}\")!");
+			}
 		}
 
 		[TearDown]