python: Better host pip options

pip by default will read system-wide and per-user configuration
files[1]. Setting PIP_CONFIG_FILE=/dev/null instructs pip to not read
any config files[2].

pip will spawn child processes of itself to do work, but not all options
are passed down to the child processes[3]. Setting global options as
environment variables[4] ensures they are passed down to any child
processes.

[1]: https://pip.pypa.io/en/stable/topics/configuration/#configuration-files
[2]: https://pip.pypa.io/en/stable/topics/configuration/#pip-config-file
[3]: https://github.com/pypa/pip/issues/9081#issue-733819665
[4]: https://pip.pypa.io/en/stable/topics/configuration/#environment-variables

Signed-off-by: Jeffery To <jeffery.to@gmail.com>

lang/python/python3-host.mk

@@ -93,6 +93,11 @@ HOST_PYTHON3_PIP:=$(STAGING_DIR_HOSTPKG)/bin/pip$(PYTHON3_VERSION)
 
 HOST_PYTHON3_PIP_CACHE_DIR:=$(DL_DIR)/pip-cache
 
+HOST_PYTHON3_PIP_VARS:= \
+	PIP_CACHE_DIR="$(HOST_PYTHON3_PIP_CACHE_DIR)" \
+	PIP_CONFIG_FILE=/dev/null \
+	PIP_DISABLE_PIP_VERSION_CHECK=1
+
 define SetupPyShim
 	if [ -f $(1)/pyproject.toml ] && [ ! -f $(1)/setup.py ] ; then \
 		$(CP) $(python3_mk_path)setup.py.shim $(1)setup.py ; \
@@ -104,11 +109,11 @@ endef
 define HostPython3/PipInstall
 	$(call locked, \
 		$(HOST_PYTHON3_VARS) \
+		$(HOST_PYTHON3_PIP_VARS) \
 		$(HOST_PYTHON3_PIP) \
-			--cache-dir "$(HOST_PYTHON3_PIP_CACHE_DIR)" \
-			--disable-pip-version-check \
 			install \
 			--no-binary :all: \
+			--progress-bar off \
 			--require-hashes \
 			$(1) \
 		$(if $(CONFIG_PYTHON3_HOST_PIP_CACHE_WORLD_READABLE), \