### What I am doing in one sentence

Checking out the branch `Update-1` from the [Roslyn github repository](https://github.com/dotnet/roslyn.git), building the csc.exe, and compiling a random Solution with the csc.exe version I just built myself.

### Expected result

I expect the performance to be comparable to the original Roslyn version which was shipped with VS 2015 Update 1, located in the path: `C:\Program Files (x86)\MSBuild\14.0\Bin`

### Actual result

The build performance of the Roslyn version I built myself is significantly worse, compared to the original one. In the solution I used in my tests: roughly 30 seconds vs. 65 seconds.

### My procedure in more detail

* Cloned <https://github.com/dotnet/roslyn.git> and checked out branch update-1
* Built Roslyn using `Release` configuration (tried with both, `Mixed Configuration` as well as `x64` for the solution platform.)
* To compile a test solution, I altered all project files to use a specific location for the csc path:

`<CscToolPath>C:\Path\To\Output\Location\Of\Roslyn\Binaries\</CscToolPath>`
* For testing purposes I am building the test solution from command line with

`MSBuild.exe /t:Rebuild /m:1 /verbosity:m MySolutionName.sln`
* I am currently also doing a clean before: 

`MSBuild.exe /t:Clean /m:1 /verbosity:m MySolutionName.sln`
* To test against the original compiler, shipped with VS 2015 Update 1, I am changing the configuration in the project files to:

`<CscToolPath>C:\Program Files (x86)\MSBuild\14.0\Bin\</CscToolPath>`

### Questions

* What can I do to to achieve a similar performance with my self-compiled Roslyn version, like with the originally shipped Roslyn dlls?
* Are there any further things (like optimizations etc.) to be considered when building Roslyn itself?