Building pthreads as native windows build

wsl-5 now compiles, so I am on to the next target: pthreads

I downloaded pthreads-w32-2.10-mingw32-pre-20160821-1-src.tar.xz

(I unpacked this with 7-zip, which complained that it was not an xz-compressed
archive, but was just a tar that had been renamed.)

it already had a makefile for gcc named GNUmakefile, so I tried it. It does
several different builds which are defined by command-line arguments.

All that I tried  failed with several undefined type errors.  The offender is int64_t:

error: unknown type name 'int64_t'

What should I do to get this to compile correctly?


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