Unlike the base vi (nvi 2.1.3), nvi-devel calls flock() on a writable
file descriptor. This has the unfortunately side effect of causing
the "Text file busy" error when you edit a script in one window and
try to run it in another.

The fix is to change the initial open() just prior to calling
file_lock() in file_init() to use O_RDONLY instead of O_RDWR. This
does not impact nvi's ability to write files, nvi creates a new
file when writing.

PR: 235445
Approved by: johans (maintainer timeout, 6 weeks), ler (mentor, implicit)