[tlbuild] [e][u]ptex rebuild from branch2019

[Karl Berry]

A serious bug has cropped up in (u)ptex. The binaries affected will be
(we believe):
  ptex, eptex, uptex, euptex,
  upbibtex, updvitype, uppltotf, uptftopl.

If you do your own commits for bin, please commit only these.
It "should" be harmless to commit others, but ...

We need to rebuild from branch2019 this time (committed in r51236),
because too many other changes have been to the trunk which would cause
possible problems.

You can get the sources from the branch to the cwd 
with subversion:
  svn co svn://tug.org/texlive/branches/branch2019/Build/source .
or with rsync:
  rsync -a --delete --exclude=.svn --exclude=Work tug.org::tlbranch .

Then ./Build or whatever you normally do should suffice. If you want to
skip compiling all the utilities,
  ./Build --disable-all-pkgs --enable-web2c
should build only the engines. (You can further add --disable-xetex,
etc., if you feel the need.) There is no harm to building everything,
though, which is probably easiest of all :).

Thanks, and happy compiling. --karl