gallium/osmesa: link with winsock2 library on Windows

To fix the MSVC build.  The build broke because we started to compile
the ddebug code on Windows after the mtypes.h changes.  Building ddebug
caused us to also use the u_network.c code for the first time.

Reviewed-by: Charmaine Lee <charmainel@vmware.com>

src/gallium/targets/osmesa/SConscript

@@ -39,6 +39,9 @@ if env['platform'] == 'windows':
         sources += ['osmesa.mingw.def']
     else:
         sources += ['osmesa.def']
+    # Link with winsock2 library
+    env.Append(LIBS = ['ws2_32'])
+
 
 gallium_osmesa = env.SharedLibrary(
     target ='osmesa',