treewide: Remove Python variants for non-Python packages

This removes Python-related build variants, and adds
PYTHON3_PKG_BUILD:=0 and minor build adjustments (where appropriate),
for non-Python packages. There should be no changes to build output.

This also updates some include paths for python3-package.mk and/or
python3-host.mk to be relative to the package Makefile.

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

libs/newt/Makefile

@@ -11,7 +11,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=newt
 PKG_VERSION:=0.52.21
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://releases.pagure.org/newt
@@ -24,6 +24,7 @@ PKG_CPE_ID:=cpe:/a:fedorahosted:newt
 
 PKG_BUILD_PARALLEL:=1
 PKG_INSTALL:=1
+PYTHON3_PKG_BUILD:=0
 
 include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/nls.mk
@@ -73,7 +74,6 @@ $(call Package/newt/Default)
   SUBMENU:=Python
   TITLE+= module for Python
   DEPENDS:=+libnewt +python3-light
-  VARIANT:=python3
 endef
 
 define Package/python3-newt/description
@@ -93,8 +93,6 @@ CONFIGURE_VARS += $(if $(CONFIG_BUILD_NLS),ac_cv_lib_c_gettext=no)
 
 MAKE_VARS+= PYTHON_CONFIG_PATH="$(STAGING_DIR)/host/bin"
 
-Build/Compile=$(call Build/Compile/Default,)
-
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include
 	$(CP) $(PKG_INSTALL_DIR)/usr/include/newt.h $(1)/usr/include/