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>
(cherry picked from commit 8c2abb7403)

lang/python/python3/Makefile

@@ -183,11 +183,11 @@ endif
 
 ifeq ($(PYTHON3_SETUPTOOLS_BUILD),1)
 define Build/Compile/python3-setuptools
+	$(HOST_PYTHON3_PIP_VARS) \
 	$(HOST_PYTHON3_PIP) \
-		--disable-pip-version-check \
-		--cache-dir "$(DL_DIR)/pip-cache" \
 		install \
 		--ignore-installed \
+		--progress-bar off \
 		--root=$(PKG_BUILD_DIR)/install-setuptools \
 		--prefix=/usr \
 		$(PKG_BUILD_DIR)/Lib/ensurepip/_bundled/setuptools-$(PYTHON3_SETUPTOOLS_VERSION)-py3-none-any.whl
@@ -201,11 +201,11 @@ endif # CONFIG_PACKAGE_python3-setuptools
 
 ifdef CONFIG_PACKAGE_python3-pip
 define Build/Compile/python3-pip
+	$(HOST_PYTHON3_PIP_VARS) \
 	$(HOST_PYTHON3_PIP) \
-		--disable-pip-version-check \
-		--cache-dir "$(DL_DIR)/pip-cache" \
 		install \
 		--ignore-installed \
+		--progress-bar off \
 		--root=$(PKG_BUILD_DIR)/install-pip \
 		--prefix=/usr \
 		$(PKG_BUILD_DIR)/Lib/ensurepip/_bundled/pip-$(PYTHON3_PIP_VERSION)-py3-none-any.whl