OK it took me all day, but I have now successfully built wireshark for x64 *and* x86
on a 64-bit PC. (Just not at the same time; I'm reusing the same source folder for now.)
For anyone else migrating from WinXP/32-bit to Win7/64-bit, the main thing you have
to make sure to get right is your environment setup, NOT necessarily anything in the
makefiles etc.
My personal "wireshark env setup" script calls SetEnv.cmd and a vcvars script to set
things up. Both of those scripts take an argument, x64 or x86. What works for me
is to call SetEnv.cmd with the right argument, then call *either* vcvarsall.bat (for x64)
*or* vcvars32.bat (for x86) with the same argument. Note that the two vcvars scripts
have slightly different paths.
I did a distclean, then a setup, then another distclean, before building all. Not certain
all of these steps are 100% necessary, but the net result was a successful build.