tor failing to build on 2018Q4 branch

[Greg Troxel <gdt%lexort.com@localhost>]

I am getting a failure updating tor on 2018Q4.  I see the same thing on
netbsd-8 earmv7hf-el and netbsd-7 i386.   It seems that a makefile
intends to make this, but it does not end up existing.



===> Building for tor-0.3.5.8
/usr/bin/make  all-am
CC       src/lib/log/libtor_log_testing_a-git_revision.o
src/lib/log/git_revision.c:15:28: fatal error: micro-revision.i: No such file or directory
compilation terminated.
*** [src/lib/log/libtor_log_testing_a-git_revision.o] Error code 1