I've fixed the above problem by adding AM_PROG_CC_C_O to configure.ac. It took some fiddling as it could not go on just any line without more errors, but it works now. I am still not convinced that I should have to do that at all; a source taken from repos should work out of the box, without alterations. In other words, the problem must be in my environment.

But now I am stumbling on the next hurdle. I get past autoconf, autoheader and auomake, only to get the following from ./configure.
Indeed, that package is nowhere to be found. A forum search for hildon-1 brings up a bunch of results, all suggesting that it should magically work in the scratchbox. Is that really the case? Is there no escape from using the scratchbox? Do I need that package if developing on the device itself?