The NetBSD-current/i386 build is working again. The following commits were made between the last failed build and the successful build:
2019.07.20.20.49.06 mrg src/external/nvidia-firmware/Makefile,v 1.3 2019.07.20.20.59.05 mrg src/sys/sys/compat_stub.h,v 1.18 Log files can be found at: http://releng.NetBSD.org/b5reports/i386/commits-2019.07.html#2019.07.20.20.59.05