[boost] path length too long for 64 bits builds

Hi, we have an issue since we have added threadapi= . On 64 bits windows machines we are seen Austin Beer said in https://github.com/boostorg/thread/pull/188#issuecomment-339829423 "FYI, the 64-bit Windows builds are failing due the unit tests exceeding the 260 character filepath limit on Windows. Every filepath includes |\msvc-14.1\debug\address-model-64\threadapi-win32\threading-multi|. Do you know if there is an easy way to shorten this? On the 32-bit builds the filepaths don't have |\address-model-64| which is just enough to keep them under the 260 character limit so they don't fail." Is there a workaround to this issue without changing the specific part of the test files folder structure? Best, Vicente