kbuild: make -r/-R effective in top Makefile for old Make versions

Backported from kernel
commit 3812b8c5c5d5 ("kbuild: make -r/-R effective in top Makefile for old Make versions")

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Makefile

@@ -12,10 +12,6 @@ NAME =
 # Comments in this file are targeted only to the developer, do not
 # expect to learn how to build the kernel reading this file.
 
-# Do not use make's built-in rules and variables
-# (this increases performance and avoids hard-to-debug behaviour)
-MAKEFLAGS += -rR
-
 # Determine target architecture for the sandbox
 include include/host_arch.h
 ifeq ("", "$(CROSS_COMPILE)")
@@ -39,15 +35,6 @@ else ifeq ("riscv64", $(MK_ARCH))
 endif
 undefine MK_ARCH
 
-# Avoid funny character set dependencies
-unexport LC_ALL
-LC_COLLATE=C
-LC_NUMERIC=C
-export LC_COLLATE LC_NUMERIC
-
-# Avoid interference with shell env settings
-unexport GREP_OPTIONS
-
 # We are using a recursive build, so we need to do a little thinking
 # to get the ordering right.
 #
@@ -64,6 +51,21 @@ unexport GREP_OPTIONS
 # descending is started. They are now explicitly listed as the
 # prepare rule.
 
+ifneq ($(sub-make-done),1)
+
+# Do not use make's built-in rules and variables
+# (this increases performance and avoids hard-to-debug behaviour)
+MAKEFLAGS += -rR
+
+# Avoid funny character set dependencies
+unexport LC_ALL
+LC_COLLATE=C
+LC_NUMERIC=C
+export LC_COLLATE LC_NUMERIC
+
+# Avoid interference with shell env settings
+unexport GREP_OPTIONS
+
 # Beautify output
 # ---------------------------------------------------------------------------
 #
@@ -137,7 +139,6 @@ export quiet Q KBUILD_VERBOSE
 
 # KBUILD_SRC is set on invocation of make in OBJ directory
 # KBUILD_SRC is not intended to be used by the regular user (for now)
-ifeq ($(KBUILD_SRC),)
 
 # OK, Make called in directory where kernel src resides
 # Do we want to locate output files in a separate directory?
@@ -168,22 +169,25 @@ $(if $(KBUILD_OUTPUT),, \
 # 'sub-make' below.
 MAKEFLAGS += --include-dir=$(CURDIR)
 
+else
+
+# Do not print "Entering directory ..." at all for in-tree build.
+MAKEFLAGS += --no-print-directory
+
+endif # ifneq ($(KBUILD_OUTPUT),)
+
 PHONY += $(MAKECMDGOALS) sub-make
 
 $(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: sub-make
 	@:
 
 sub-make: FORCE
-	$(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \
+	$(Q)$(MAKE) sub-make-done=1 \
+	$(if $(KBUILD_OUTPUT),-C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR)) \
 	-f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))
 
-# Leave processing to above invocation of make
+else # sub-make-done
-skip-makefile := 1
-endif # ifneq ($(KBUILD_OUTPUT),)
-endif # ifeq ($(KBUILD_SRC),)
-
 # We process the rest of the Makefile if this is the final invocation of make
-ifeq ($(skip-makefile),)
 
 # Do not print "Entering directory ...",
 # but we want to display it when entering to the output directory
@@ -2546,7 +2550,7 @@ $(cmd_files): ;        # Do not try to update included dependency files
 
 endif    #ifeq ($(config-targets),1)
 endif    #ifeq ($(mixed-targets),1)
-endif	# skip-makefile
+endif	 # sub-make-done
 
 PHONY += FORCE
 FORCE: