Revert r351833 and r352250.

They were breaking the Windows build when using MSBuild, see the
discussion on D56781.

r351833: "Use response file when generating LLVM-C.dll"

> Use response file when generating LLVM-C.dll
>
> As discovered in D56774 the command line gets to long, so use a response file to give the script the libs. This change has been tested and is confirmed working for me.
>
> Commited on behalf of Jakob Bornecrantz
>
> Differential Revision: https://reviews.llvm.org/D56781

r352250: "Build LLVM-C.dll by default on windows and enable in release package"

>  Build LLVM-C.dll by default on windows and enable in release package
>
>  With the fixes to the building of LLVM-C.dll in D56781 this should now
>  be safe to land. This will greatly simplify dealing with LLVM for people
>  that just want to use the C API on windows. This is a follow up from
>  D35077.
>
>  Patch by Jakob Bornecrantz!
>
>  Differential revision: https://reviews.llvm.org/D56774

llvm-svn: 352492