The following is copied from the Readme.txt in the Sourcecode\RuntimeLibraries folder:
To build the libraries, use the predefined .cmd files. They require a vsvars3210.bat file, which is simply the copy of vsvars32.bat but for the .NET 1.0 SDK. For .NET 2.0 builds, a vsvars3220.bat file has to be available.
To build .NET 3.5 specific builds of the LinqSupportClasses sourcecode, please see the LinqSupportClasses folder for details: either use the VS.NET 2008 specific sln file or use the .cmd files.
The source code references a strong key, which is not shipped with the code. You should remove these references in the AssemblyInfo***.cs classes.