The names of the directories holding the per-platform libs & dlls for Windows, x86_32 and x86_64, do not match the names provided by macros in a wide range of MSVS versions. Those names are Win32 and x64 and are the values of $(PlatformName) in all versions of MSVS since 64-bit was introduced and $(Platform), available since MSVS 2008.
The only macro available to use with the current naming scheme is $(PlatformArchitecture) which has values of 32 or 64. That is available in MSVS 2013 but not in MSVS 2008. I do not have 2010 or 2012 so I cannot confirm when it was introduced.
Being able to use macros makes it easier to set up build systems and is critical when using GYP because in GYP it is not possible to provide per-configuration/platform library names or directories.
Please change the names to Win32 and x64.