Always include interpreter constraints in PEXes.

Previously we left them off for internal only PEXes. Leaving them does
no harm since PEX uses the current interpreter if it matches constraints
and it aids in the debugability of process chroots.

[ci skip-rust]
[ci skip-build-wheels]

src/python/pants/backend/python/util_rules/pex.py

@@ -534,16 +534,14 @@ async def build_pex(
  # constraints.
  argv.extend(request.platforms.generate_pex_arg_list())
  else:
+ argv.extend(request.interpreter_constraints.generate_pex_arg_list())
  # NB: If it's an internal_only PEX, we do our own lookup of the interpreter based on the
  # interpreter constraints, and then will run the PEX with that specific interpreter. We
  # will have already validated that there were no platforms.
- # Otherwise, we let Pex resolve the constraints.
  if request.internal_only:
  python = await Get(
  PythonExecutable, PexInterpreterConstraints, request.interpreter_constraints
  )
- else:
- argv.extend(request.interpreter_constraints.generate_pex_arg_list())
 
  argv.append("--no-emit-warnings")