unison-2.48 build fails with latest ocaml and flexdll

[Andrew Schulman]

I'm trying to build unison 2.48.3, which worked fine the last time I tried
it, in June 2015.  Today the build fails, with "flexdll error: cannot
relocate":

>>> Compiling unison2.48-2.48.3-2.x86_64
ocamlc -o mkProjectInfo unix.cma str.cma mkProjectInfo.ml
File "mkProjectInfo.ml", line 1:
Error: Error on dynamically loaded library:
/usr/lib/ocaml/stublibs/dllunix.so: flexdll error: cannot relocate
RELOC_REL32, target is too far: 0xfffffffc0f997112  0xf997112

I ran /bin/rebaseall and tried again, with the same result.

Does anyone know the solution?

Thanks,
Andrew

cygwin 2.5.0-1
flexdll 0.34-1
ocaml 4.02.3-2