Kbuild fixes for v5.3

- add compile_commands.json to .gitignore
 
  - fix false-positive warning from gen_compile_commands.py after
    allnoconfig build
 
  - remove unused code
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Merge tag 'kbuild-fixes-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - add compile_commands.json to .gitignore

 - fix false-positive warning from gen_compile_commands.py after
   allnoconfig build

 - remove unused code

* tag 'kbuild-fixes-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: remove unused single-used-m
  gen_compile_commands: lower the entry count threshold
  .gitignore: Add compilation database file
  kbuild: remove unused objectify macro

.gitignore

@@ -142,3 +142,6 @@ x509.genkey
 
 # Kdevelop4
 *.kdev4
+
+# Clang's compilation database file
+/compile_commands.json

scripts/Kbuild.include

@@ -190,9 +190,6 @@ echo-cmd = $(if $($(quiet)cmd_$(1)),\
 # printing commands
 cmd = @set -e; $(echo-cmd) $(cmd_$(1))
 
-# Add $(obj)/ for paths that are not absolute
-objectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o)))
-
 ###
 # if_changed      - execute command if any prerequisite is newer than
 #                   target, or command line has changed

scripts/Makefile.lib

@@ -45,7 +45,6 @@ subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
 multi-used-y := $(sort $(foreach m,$(obj-y), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))), $(m))))
 multi-used-m := $(sort $(foreach m,$(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y)) $($(m:.o=-m))), $(m))))
 multi-used   := $(multi-used-y) $(multi-used-m)
-single-used-m := $(sort $(filter-out $(multi-used-m),$(obj-m)))
 
 # $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
 # tell kbuild to descend
@@ -91,7 +90,6 @@ lib-y		:= $(addprefix $(obj)/,$(lib-y))
 subdir-obj-y	:= $(addprefix $(obj)/,$(subdir-obj-y))
 real-obj-y	:= $(addprefix $(obj)/,$(real-obj-y))
 real-obj-m	:= $(addprefix $(obj)/,$(real-obj-m))
-single-used-m	:= $(addprefix $(obj)/,$(single-used-m))
 multi-used-m	:= $(addprefix $(obj)/,$(multi-used-m))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 

scripts/gen_compile_commands.py

@@ -21,9 +21,9 @@ _LINE_PATTERN = r'^cmd_[^ ]*\.o := (.* )([^ ]*\.c)$'
 _VALID_LOG_LEVELS = ['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL']
 
 # A kernel build generally has over 2000 entries in its compile_commands.json
-# database. If this code finds 500 or fewer, then warn the user that they might
+# database. If this code finds 300 or fewer, then warn the user that they might
 # not have all the .cmd files, and they might need to compile the kernel.
-_LOW_COUNT_THRESHOLD = 500
+_LOW_COUNT_THRESHOLD = 300
 
 
 def parse_arguments():