The NetBSD-current/i386 build is working again. The following commits were made between the last failed build and the successful build:
2018.03.15.03.13.51 christos src/sys/compat/common/Makefile.sysio,v 1.8 2018.03.15.03.13.51 christos src/sys/compat/common/compat_mod.c,v 1.25 2018.03.15.03.13.51 christos src/sys/compat/common/uvm_13.c,v 1.1 2018.03.15.03.13.51 christos src/sys/compat/common/uvm_50.c,v 1.1 2018.03.15.03.13.51 christos src/sys/compat/sys/uvm.h,v 1.1 2018.03.15.03.21.58 christos src/sys/uvm/uvm_swap.c,v 1.177 2018.03.15.03.21.58 christos src/sys/uvm/uvm_swap.h,v 1.24 2018.03.15.03.22.23 christos src/sys/compat/sys/uvm.h,v 1.2 2018.03.15.03.45.05 ozaki-r src/sys/arch/x86/x86/db_memrw.c,v 1.5 Log files can be found at: http://releng.NetBSD.org/b5reports/i386/commits-2018.03.html#2018.03.15.03.45.05