helper function / @rule to inject environment variables with absolute paths into hermetic process executions

[cosmicexplorer]

#8036 (comment) describes one case where we wanted to be able to use a feature (a java agent) which required setting the runtime library path (DY)?LD_LIBRARY_PATH variable to make a compiled shared library available to the java invocation. We were able to work around this issue by using the -agentpath: option instead, but in general there are many settings for many programs, typically set via environment variables, which require absolute paths on most operating systems (such as PATH, CPATH, LIBRARY_PATH, and other variables used to configure compilation of C/C++ code).

See #6893 for another place we want to use these variables, and work around it by instead invoking /bin/sh to interpret a lengthy generated command line:

pants/src/python/pants/backend/jvm/subsystems/graal.py

Lines 243 to 247 in 24727b2

	result = yield Get(ExecuteProcessResult, ExecuteProcessRequest(
	argv=tuple([
	'/bin/sh', '-c',
	' && '.join(sub_commands),
	]),

^The above is a little brittle, and #8036 (comment) describes one bikesheddable alternative -- a helper function or @rule:

def execute_process_with_env_vars_interpolated(execute_process_request, env_to_command):
  with temporary_directory() as tempdir:
    with open(os.path.join(tempdir, "script"), "w") as f:
      lines = ["{key}={value}".format(key=key, value=value) for key, value in sorted(env_to_command.items())]
      lines.append("exec " + shlex(execute_process_request.argv))
      f.write("\n".join(lines))
    captured_directory_digest = capture(tempdir, "script")
    merged_directory_digest = merge(captured_directory_digest, execute_process_request.directory_digest)
  return execute_process_request.with(argv="./script", directory_digest=merged_directory_digest)

[Eric-Arellano]

This is achieved via PantsEnvironment, and I believe also BinaryPaths.