package/pkg-python: <pkg>_SUBDIR cleanup

No functional change is brought by this modification.

This patch:
* removes redundant <pkg>_SRCDIR and <pkg>_BUILDDIR declarations
  (already defined in pkg-generic.mk)
* documents the usage of <pkg>_SUBDIR in the python-specific section of
  the manual.

Signed-off-by: Lionel Orry <lionel.orry@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

docs/manual/adding-packages-python.txt

@@ -113,6 +113,12 @@ optionally be defined, depending on the package's needs. Many of them
 are only useful in very specific cases, typical packages will
 therefore only use a few of them, or none.
 
+* +PYTHON_FOO_SUBDIR+ may contain the name of a subdirectory inside the
+  package that contains the main +setup.py+ file. This is useful,
+  if for example, the main +setup.py+ file is not at the root of
+  the tree extracted by the tarball. If +HOST_PYTHON_FOO_SUBDIR+ is not
+  specified, it defaults to +PYTHON_FOO_SUBDIR+.
+
 * +PYTHON_FOO_ENV+, to specify additional environment variables to
   pass to the Python +setup.py+ script (for both the build and install
   steps). Note that the infrastructure is automatically passing

package/pkg-python.mk

@@ -105,9 +105,6 @@ HOST_PKG_PYTHON_SETUPTOOLS_INSTALL_OPTS = \
 
 define inner-python-package
 
-$(2)_SRCDIR	= $$($(2)_DIR)/$$($(2)_SUBDIR)
-$(2)_BUILDDIR	= $$($(2)_SRCDIR)
-
 $(2)_ENV         ?=
 $(2)_BUILD_OPTS   ?=
 $(2)_INSTALL_OPTS ?=