crossdev failed trying to build linux headers for a cross-compile to i586. environment 'ARCH' gets set to x86 (a portage arch name) but make defconfig needs ARCH=i386. Fix is to use ${xmakeopts} which is already set up correctly for the previous 'make mrproper'. Problem exists in kernel-2.eclass v1.172
Created attachment 86141 [details, diff] patch to kernel-2.eclass
Not a portage bug
this was fixed about this time yesterday, please emerge sync and re-try.