python3: Add Py3Build/InstallBuildDepends recipe

This adds a recipe, Py3Build/InstallBuildDepends, that installs the
requirements listed in HOST_PYTHON3_PACKAGE_BUILD_DEPENDS. This allows
other (non-Python) packages to install host Python packages by calling
this recipe, without having to know the internals of python3-package.mk.

This also updates apparmor to call this recipe.

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

lang/python/README.md

@@ -369,3 +369,30 @@ HOST_PYTHON3_PACKAGE_BUILD_DEPENDS:=setuptools-scm
 ```
 
 The Python package will be installed in `$(STAGING_DIR_HOSTPKG)/lib/pythonX.Y/site-packages`.
+
+#### Non-Python packages installing host-side Python packages
+
+Non-Python packages can also install host-side Python packages using the same mechanism:
+
+* Set `HOST_PYTHON3_PACKAGE_BUILD_DEPENDS` (see above for details).
+
+* Include `python3-package.mk` (set `PYTHON3_PKG_BUILD:=0` to avoid using the default Python package build recipes).
+
+* Call `Py3Build/InstallBuildDepends` to initiate the installation.
+
+For example:
+
+```
+PYTHON3_PKG_BUILD:=0
+HOST_PYTHON3_PACKAGE_BUILD_DEPENDS:=setuptools-scm
+
+include $(INCLUDE_DIR)/package.mk
+include ../../lang/python/python3-package.mk
+# If outside of the packages feed:
+# include $(TOPDIR)/feeds/packages/lang/python/python3-package.mk
+
+define Build/Compile
+	$(call Py3Build/InstallBuildDepends)
+	$(call Build/Compile/Default)
+endef
+```

lang/python/python3-package.mk

@@ -215,10 +215,14 @@ define Py3Build/CheckHostPipVersionMatch
 endef
 endif
 
-define Py3Build/Compile/Default
+define Py3Build/InstallBuildDepends
 	$(if $(PYTHON3_PKG_HOST_PIP_INSTALL_ARGS), \
 		$(call HostPython3/PipInstall,$(PYTHON3_PKG_HOST_PIP_INSTALL_ARGS)) \
 	)
+endef
+
+define Py3Build/Compile/Default
+	$(call Py3Build/InstallBuildDepends)
 	$(call Python3/ModSetup, \
 		$(PYTHON3_PKG_SETUP_DIR), \
 		$(PYTHON3_PKG_SETUP_GLOBAL_ARGS) \

utils/apparmor/Makefile

@@ -132,9 +132,7 @@ endef
 
 define Build/Install
 	# Make sure we have python's setup tools installed
-	$(if $(PYTHON3_PKG_HOST_PIP_INSTALL_ARGS), \
-		$(call HostPython3/PipInstall,$(PYTHON3_PKG_HOST_PIP_INSTALL_ARGS)) \
-	)
+	$(call Py3Build/InstallBuildDepends)
 	$(INSTALL_DIR) $(PKG_INSTALL_DIR)-libapparmor $(PKG_INSTALL_DIR)-utils $(PKG_INSTALL_DIR)-profiles
 	# Installing libapparmor
 	+$(MAKE_VARS) PYTHON=$(HOST_PYTHON) VERSION=$(PYTHON3_VERSION) \