nmake script wrong main build target output filename
In src/or/Makefile.nmake build target "tor.exe", the commandline does not include an output filename parameter. MSVC's cl.exe does a strange thing and guesses the output filename based on the last thing on the list, which in this case is tor_main.obj. This means that the build output is tor_main.exe, not tor.exe.
To specify an output filename, add /Fe followed by the filename - without a space inbetween - somewhere into the commandline. In this case it would be /Fetor.exe.
PS: According to google search nmake supports the standard make token for 'rule target', implying that /Fe$@ (for compiler) and /out$@ (for linker) could work and might be useful in a future cleanup.