xapian core missing link to math on MSYS2

[Olly Betts]

On Wed, Mar 15, 2017 at 10:05:31AM +0100, Mario Emmenlauer wrote:
> I've tried to build xapian-core 1.4.3 on MSYS2. It fails with attached
> error (undefined reference to `exp10').

The issue is that exp10() isn't a standard function.  This is fixed in
git already, so should work with the next release:

https://trac.xapian.org/changeset/8ac975a135e2571d78eaa82e63974509877d3110/git

There's only one use of exp10() currently, so the simplest workaround is
probably to patch api/omenquire.cc to use __builtin_exp10(x) or pow(10.0, x)
instead of exp10(x) (the former requires GCC).

Cheers,
    Olly