cmake: tweak static library names to avoid conflict

MSVC was trying to write both the static library and the DLL shim loader to
x265.lib.  After this change, the static library is now x265-static.lib and
the shim loader is x265.lib (corresponding with x265.dll)

--HG--
extra : amend_source : e3c0e4f0bab8626999d4b28046437281aab2cbbb
cmake: fixes for non-assembly builds and windows builds
cmake: this time for reals