cryptsetup was originaly using kernel-mod to check within the .config file for DM_CRYPT however kernel-mod doesn't appear to support the setting of KBUILD_OUTPUT for the kernel output directory at the moment small modification to use linux-mod / linux_chkconfig_present / KV_OUT_DIR instead.
Created attachment 56315 [details, diff] patch to cryptsetup-0.1-r1.ebuild
Created attachment 58363 [details, diff] patches various functions in kernel-mod.eclass to use KBUILD_OUTPUT instead of hard-coded /usr/src/linux trivially patches the following functions to use KBUILD_OUTPUT instead of KERNEL_DIR or a hardcoded '/usr/src/linux': kernel-mod_configoption_present kernel-mod_configoption_module kernel-mod_configoption_builtin kernel-mod_checkzlibinflate_configured fixes ebuilds of cryptsetup, svgalib, etc.
Fixed in CVS though I used linux-info and did it slightly differently.