In generated text fixture location lookup code:
When the second argument to write_file() is a list, it is written one
item per line to the path specified by the first argument. This ensures
that we emit a trailing newline at EOF to comply with -Wnewline-eof.

Elsewhere:
Lack of a newline at EOF was undefined behaviour prior to C++11. The
Fuchsia tree sets -Wnewline-eof in its buildroot, so we plan to do the
same. This cleans up remaining first-party C++ sources that don't
include a trailing newline.