[Xamarin.Android.Bcl-Tests] Run only in Debug configuration

Commit d1d9820 enabled `Xamarin.Android.Bcl-Tests` to build and run
in the Release configuration. This was the right idea, but the wrong
time: [The Jenkins build for xamarin-android/d0d8640b][xad0] reports
68 failures, due to running the `Xamarin.Android.Bcl-Tests` in the
Release configuration, in which the linker is *enabled*.

[xad0]: https://jenkins.mono-project.com/view/Xamarin.Android/job/xamarin-android/666/

Enabling the linker is breaking these tests. :-(

This needs to be addressed -- enabling the linker should *not* break
the BCL unit tests! -- but in the meantime, partially revert commit
d1d9820 and only run the BCL unit tests in the Debug configuration,
removing this source of unit test failures.

Author: jonpryor

Makefile

@@ -161,7 +161,6 @@ TEST_APK_PROJECTS = \
 
 TEST_APK_PROJECTS_RELEASE = \
 	src/Mono.Android/Test/Mono.Android-Tests.csproj \
-	tests/Xamarin.Android.Bcl-Tests/Xamarin.Android.Bcl-Tests.csproj \
 	tests/Xamarin.Forms-Performance-Integration/Droid/Xamarin.Forms.Performance.Integration.Droid.csproj
 
 # Syntax: $(call BUILD_TEST_APK,path/to/project.csproj,additional_msbuild_flags)

tests/RunApkTests.targets

@@ -19,7 +19,7 @@
     `$(TEST_APK_PROJECTS_RELEASE)` within the toplevel `Makefile`.
     -->
   <Import Project="..\src\Mono.Android\Test\Mono.Android-Tests.projitems" />
-  <Import Project="..\tests\Xamarin.Android.Bcl-Tests\Xamarin.Android.Bcl-Tests.projitems" />
+  <Import Project="..\tests\Xamarin.Android.Bcl-Tests\Xamarin.Android.Bcl-Tests.projitems" Condition=" '$(Configuration)' == 'Debug' " />
   <Import Project="..\tests\CodeGen-Binding\Xamarin.Android.JcwGen-Tests\Xamarin.Android.JcwGen-Tests.projitems" Condition=" '$(Configuration)' == 'Debug' " />
   <Import Project="..\tests\locales\Xamarin.Android.Locale-Tests\Xamarin.Android.Locale-Tests.projitems"  Condition=" '$(Configuration)' == 'Debug' " />
   <Import Project="..\tests\Xamarin.Forms-Performance-Integration\Droid\Xamarin.Forms.Performance.Integration.Droid.projitems"  Condition=" '$(Configuration)' == 'Release' And '$(AotAssemblies)' != 'true' " />