See build log
Created attachment 251025 [details]
Fixed. Thanks for reporting.
I missed that there are two Makefiles (Makefile and Imakefile) to check for the LDFLAGS problem - and the file in use depends on the IUSE=X flag.
+ 19 Oct 2010; Thomas Beierlein <firstname.lastname@example.org> ibp-0.21.ebuild,
+ Make Imakefile respect LDFLAGS (bug #341475)
Archtested on x86: Everything fine