tests/test-diff-newlines.t

pyoxidizer: force pip to not use pep517 in order to be able to install hg

Mercurial is not (yet) a pep517 package, but the presence of a pyproject.toml
file tells newer-ish versions of pip that it should be one.

This is related to 58fe6d127a01, and fixes pyoxidizer builds for the Heptapod
CI.

Differential Revision: https://phab.mercurial-scm.org/D11710

  $ hg init

  $ "$PYTHON" -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
  $ hg ci -Ama -d '1 0'
  adding a

  $ echo clean diff >> a
  $ hg ci -mb -d '2 0'

  $ hg diff -r0 -r1
  diff -r 107ba6f817b5 -r 310ce7989cdc a
  --- a/a	Thu Jan 01 00:00:01 1970 +0000
  +++ b/a	Thu Jan 01 00:00:02 1970 +0000
  @@ -1,2 +1,3 @@
   confuse str.splitlines
   embedded\r (no-eol) (esc)
  newline
  +clean diff