pkg-configconfig files not being recognised by the package, despite appearing the the RPM spec file manifest.
After a certain amount of bafflement, I noticed the problem file wasn't being installed in the correct location within the RPM build-root; instead it was being installed in a subdirectory of the build-root whose structure doubled the build-root tree.
Makefile.am more closely, I quickly located the source of the problem:
bindir = $(DESTDIR)@bindir@
libdir = $(DESTDIR)@libdir@
pkgconfigdir = $(DESTDIR)$(libdir)/pkgconfig
$(DESTDIR), which is set to the build-root by RPM, has been added to the path of the
libdir macro, including it for a second time in the
pkgconfigdir macro has the effect of duplicating the build-root hierarchy, causing the manifest match to fail.
Fortunately all it took was a quick patch to snip out the extra reference, and everything built as expected — it's just annoying it took me as long as it did to notice the problem...