scripts/kernel-doc.py: don't create *.pyc files

As reported by Andy, kernel-doc.py is creating a __pycache__
directory at build time.

Disable creation of __pycache__ for the libraries used by
kernel-doc.py, when excecuted via the build system or via
scripts/find-unused-docs.sh.

Reported-by: Andy Shevchenko <[e-mail]>
Closes: https://lore.kernel.org/linux-doc/[e-mail]/
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>
Tested-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>
Message-ID: <158b96[e-mail]>

drivers/gpu/drm/Makefile

···
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = \
 		$(CC) $(c_flags) -fsyntax-only -x c /dev/null -include $< -include $<; \
-		$(srctree)/scripts/kernel-doc -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
+		 PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
 		touch $@
 
 $(obj)/%.hdrtest: $(src)/%.h FORCE

drivers/gpu/drm/i915/Makefile

···
 #
 # Enable locally for CONFIG_DRM_I915_WERROR=y. See also scripts/Makefile.build
 ifdef CONFIG_DRM_I915_WERROR
-    cmd_checkdoc = $(srctree)/scripts/kernel-doc -none -Werror $<
+    cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none -Werror $<
 endif
 
 # header test

include/drm/Makefile

···
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = \
 		$(CC) $(c_flags) -fsyntax-only -x c /dev/null -include $< -include $<; \
-		$(srctree)/scripts/kernel-doc -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
+		PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
 		touch $@
 
 $(obj)/%.hdrtest: $(src)/%.h FORCE

scripts/Makefile.build

···
 endif
 
 ifneq ($(KBUILD_EXTRA_WARN),)
-  cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $(KDOCFLAGS) \
+  cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(KDOCFLAGS) \
         $(if $(findstring 2, $(KBUILD_EXTRA_WARN)), -Wall) \
         $<
 endif

scripts/find-unused-docs.sh

···
 	if [[ ${FILES_INCLUDED[$file]+_} ]]; then
 	continue;
 	fi
-	str=$(scripts/kernel-doc -export "$file" 2>/dev/null)
+	str=$(PYTHONDONTWRITEBYTECODE=1 scripts/kernel-doc -export "$file" 2>/dev/null)
 	if [[ -n "$str" ]]; then
 	echo "$file"
 	fi