Drop --build-dir from the CLI

This was restored as a no-op for PyCharm, as a way to soften the
migration for them. It is no longer necessary, since the migration has
completed.

src/pip/_internal/cli/base_command.py

@@ -148,20 +148,6 @@ def _main(self, args: List[str]) -> int:
                 )
                 options.cache_dir = None
 
-        if getattr(options, "build_dir", None):
-            deprecated(
-                reason=(
-                    "The -b/--build/--build-dir/--build-directory "
-                    "option is deprecated and has no effect anymore."
-                ),
-                replacement=(
-                    "use the TMPDIR/TEMP/TMP environment variable, "
-                    "possibly combined with --no-clean"
-                ),
-                gone_in="21.3",
-                issue=8333,
-            )
-
         if "2020-resolver" in options.features_enabled:
             logger.warning(
                 "--use-feature=2020-resolver no longer has any effect, "

src/pip/_internal/cli/cmdoptions.py

@@ -719,18 +719,6 @@ def _handle_no_cache_dir(
     help="Don't install package dependencies.",
 )
 
-build_dir: Callable[..., Option] = partial(
-    PipOption,
-    "-b",
-    "--build",
-    "--build-dir",
-    "--build-directory",
-    dest="build_dir",
-    type="path",
-    metavar="dir",
-    help=SUPPRESS_HELP,
-)
-
 ignore_requires_python: Callable[..., Option] = partial(
     Option,
     "--ignore-requires-python",

src/pip/_internal/commands/download.py

@@ -37,7 +37,6 @@ class DownloadCommand(RequirementCommand):
     def add_options(self) -> None:
         self.cmd_opts.add_option(cmdoptions.constraints())
         self.cmd_opts.add_option(cmdoptions.requirements())
-        self.cmd_opts.add_option(cmdoptions.build_dir())
         self.cmd_opts.add_option(cmdoptions.no_deps())
         self.cmd_opts.add_option(cmdoptions.global_options())
         self.cmd_opts.add_option(cmdoptions.no_binary())

src/pip/_internal/commands/install.py

@@ -135,8 +135,6 @@ def add_options(self) -> None:
             ),
         )
 
-        self.cmd_opts.add_option(cmdoptions.build_dir())
-
         self.cmd_opts.add_option(cmdoptions.src())
 
         self.cmd_opts.add_option(

src/pip/_internal/commands/wheel.py

@@ -65,7 +65,6 @@ def add_options(self) -> None:
         self.cmd_opts.add_option(cmdoptions.src())
         self.cmd_opts.add_option(cmdoptions.ignore_requires_python())
         self.cmd_opts.add_option(cmdoptions.no_deps())
-        self.cmd_opts.add_option(cmdoptions.build_dir())
         self.cmd_opts.add_option(cmdoptions.progress_bar())
 
         self.cmd_opts.add_option(