Static build on windows results in redundant symbols

[Geoff Evans]

Windows 7 x64 - 1.8.0 complete source package

The makepanda build script tells link.exe to archive panda .lib files along with the .obj files output from cl. This makes sense when building dlls since those libs are just dll-import stub libraries (the real code staying in the dll, not the lib). However, when building panda as a static lib you don't want to have the link step join all the different panda libs together. If you do it causes heinous linker warnings about duplicate symbols, and in some circumstances can overflow the size .lib file that link.exe is capable of writing (somewhere on the high-order of hundreds of megs I think). When linking an application against panda3d when built as a static library, it should be up to the exe/dll to link the appropriate .lib files (and thirdparty lib files).

https://github.com/gorlak/panda3d/commit/c07ada7cd976f5837c4628b8c46efbb1e880a0c3