Bug#945943: exim4: FTBFS on hurd-i386: "operating system GNU is not supported"

[Paul Sonnenschein <paul@sonnenschein.ruhr>]

Source: exim4
Severity: important
Version: 4.93~RC5-1
User: debian-hurd@lists.debian.org
Usertags: hurd
X-Debbugs-CC: debian-hurd@lists.debian.org

Hello,

exim4 fails to build from source on hurd-i386 with the message:

> *** Sorry - operating system GNU is not supported
> *** See OS/Makefile-* for supported systems

See [1] for the complete build log.

It however builds successfully if the files OS/unsupported/*-GNU are
moved into the directory OS/.

Could you take a look?

Thanks.

[1]: 
https://buildd.debian.org/status/fetch.php?pkg=exim4&arch=hurd-i386&ver=4.93%7ERC5-1&stamp=1574915162&raw=0