$ REBUILD_CHECK=1 mach build faster                                                                                                                                                                                                       
 0:00.67 Clobber not needed.
 Input not found: /home/emilio/src/moz/gecko-5/python/mozbuild/mozbuild/virtualenv.py
 0:00.67 /home/emilio/.mozbuild/_virtualenvs/mach/bin/python /home/emilio/src/moz/gecko-5/configure.py
 0:00.86 Re-executing in the virtualenv
 0:01.05 Adding configure options from /home/emilio/src/moz/gecko-5/.mozconfig
 0:01.05   --enable-artifact-builds
 0:01.05   --enable-debug
 0:01.05   MOZBUILD=/home/emilio/.mozbuild
 0:01.05   MOZCONFIGS=/home/emilio/dotfiles/common/.mozconfigs/mozconfigs
 0:01.05   ARTIFACT_BUILD=1
 0:01.05 checking for vcs source checkout... git
....

It was moved in bug 1732948.

Patch incoming. You beat me to it 😁
Side-note: I'd recommend doing ./mach ... instead of mach ... so that Mach doesn't use Python sources from one tree, but related non-Python files from the other. This is mostly an issue when handling multiple trees.

(We used to recommend adding Mach to the $PATH before Python shenanigans were better-understand, is what I'm piecing together here in 2021).

(In reply to Mitchell Hentges [:mhentges] 🦀 from comment #2)

Patch incoming.
Side-note: I'd recommend doing ./mach ... instead of mach ... so that Mach doesn't use Python sources from one tree, but related non-Python files from the other. This is mostly an issue when handling multiple trees.

(We used to recommend adding Mach to the $PATH before Python shenanigans were better-understand, is what I'm piecing together here in 2021).

FWIW I don't have mach in $PATH, instead I have:

mach() {
  local tree=$(git rev-parse --show-toplevel 2>/dev/null || hg root 2>/dev/null)
  if [ -f "$tree/mach" ]; then
    "$tree/mach" "$@"
  else
    echo "Not in a mozilla tree"
  fi
}

In my shell config, which does the right thing :-)

https://hg.mozilla.org/mozilla-central/rev/1ef6c9bb62b9

https://hg.mozilla.org/mozilla-central/rev/f9b4ccef00db

Set release status flags based on info from the regressing bug 1732948