Kbuild updates for v5.1

- do not generate unneeded top-level built-in.a
 
  - let git ignore O= directory entirely
 
  - optimize scripts/kallsyms slightly
 
  - exclude DWARF info from *.s regardless of config options
 
  - fix GCC toolchain search path for Clang to prepare ld.lld support
 
  - do not generate modules.order when CONFIG_MODULES is disabled
 
  - simplify single target rules and remove VPATH for external module build
 
  - allow to add optional flags to dpkg-buildpackage when building deb-pkg
 
  - move some compiler option tests from Makefile to Kconfig
 
  - various Makefile cleanups
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Merge tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - do not generate unneeded top-level built-in.a

 - let git ignore O= directory entirely

 - optimize scripts/kallsyms slightly

 - exclude DWARF info from *.s regardless of config options

 - fix GCC toolchain search path for Clang to prepare ld.lld support

 - do not generate modules.order when CONFIG_MODULES is disabled

 - simplify single target rules and remove VPATH for external module
   build

 - allow to add optional flags to dpkg-buildpackage when building
   deb-pkg

 - move some compiler option tests from Makefile to Kconfig

 - various Makefile cleanups

* tag 'kbuild-v5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (40 commits)
  kbuild: remove scripts/basic/% build target
  kbuild: use -Werror=implicit-... instead of -Werror-implicit-...
  kbuild: clean up scripts/gcc-version.sh
  kbuild: remove cc-version macro
  kbuild: update comment block of scripts/clang-version.sh
  kbuild: remove commented-out INITRD_COMPRESS
  kbuild: move -gsplit-dwarf, -gdwarf-4 option tests to Kconfig
  kbuild: [bin]deb-pkg: add DPKG_FLAGS variable
  kbuild: move ".config not found!" message from Kconfig to Makefile
  kbuild: invoke syncconfig if include/config/auto.conf.cmd is missing
  kbuild: simplify single target rules
  kbuild: remove empty rules for makefiles
  kbuild: make -r/-R effective in top Makefile for old Make versions
  kbuild: move tools_silent to a more relevant place
  kbuild: compute false-positive -Wmaybe-uninitialized cases in Kconfig
  kbuild: refactor cc-cross-prefix implementation
  kbuild: hardcode genksyms path and remove GENKSYMS variable
  scripts/gdb: refactor rules for symlink creation
  kbuild: create symlink to vmlinux-gdb.py in scripts_gdb target
  scripts/gdb: do not descend into scripts/gdb from scripts
  ...

Kbuild

@@ -1,16 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # Kbuild for top-level directory of the kernel
-# This file takes care of the following:
-# 1) Generate bounds.h
-# 2) Generate timeconst.h
-# 3) Generate asm-offsets.h (may need bounds.h and timeconst.h)
-# 4) Check for missing system calls
-# 5) check atomics headers are up-to-date
-# 6) Generate constants.py (may need bounds.h)
 
 #####
-# 1) Generate bounds.h
+# Generate bounds.h
 
 bounds-file := include/generated/bounds.h
 
@@ -21,7 +14,7 @@ $(bounds-file): kernel/bounds.s FORCE
 	$(call filechk,offsets,__LINUX_BOUNDS_H__)
 
 #####
-# 2) Generate timeconst.h
+# Generate timeconst.h
 
 timeconst-file := include/generated/timeconst.h
 
@@ -33,8 +26,7 @@ $(timeconst-file): kernel/time/timeconst.bc FORCE
 	$(call filechk,gentimeconst)
 
 #####
-# 3) Generate asm-offsets.h
-#
+# Generate asm-offsets.h
 
 offsets-file := include/generated/asm-offsets.h
 
@@ -47,8 +39,7 @@ $(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
 	$(call filechk,offsets,__ASM_OFFSETS_H__)
 
 #####
-# 4) Check for missing system calls
-#
+# Check for missing system calls
 
 always += missing-syscalls
 targets += missing-syscalls
@@ -60,8 +51,7 @@ missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
 	$(call cmd,syscalls)
 
 #####
-# 5) Check atomic headers are up-to-date
-#
+# Check atomic headers are up-to-date
 
 always += old-atomics
 targets += old-atomics
@@ -72,14 +62,5 @@ quiet_cmd_atomics = CALL    $<
 old-atomics: scripts/atomic/check-atomics.sh FORCE
 	$(call cmd,atomics)
 
-#####
-# 6) Generate constants for Python GDB integration
-#
-
-extra-$(CONFIG_GDB_SCRIPTS) += build_constants_py
-
-build_constants_py: $(timeconst-file) $(bounds-file)
-	@$(MAKE) $(build)=scripts/gdb/linux $@
-
 # Keep these three files during make clean
 no-clean-files := $(bounds-file) $(offsets-file) $(timeconst-file)