[tests] Fix XMake_Tests.ConfigurationInvalid for mono/osx
[tests] Fix XMake_Tests.ConfigurationInvalid for mono/osx

Use RunnerUtilities.PathToCurrentlyRunningMsBuildExe to get the actual
executable filename, instead of hardcoding `msbuild.exe`.

mono/msbuild,mono/msbuild,mono/msbuild,mono/msbuild