kbuild: include Makefile.compiler only when compiler is needed

Since commit f2f02ebd8f38 ("kbuild: improve cc-option to clean up all
temporary files"), running 'make kernelversion' in a read-only source
tree emits a bunch of warnings:

  mkdir: cannot create directory '.tmp_12345': Permission denied

No-build targets such as kernelversion, clean, help, etc. do not
need to evaluate $(call cc-option,) or friends. Skip Makefile.compiler
so $(call cc-option,) becomes no-op.

This not only fixes the warnings, but also runs non-build targets much
faster.

Basically, all installation targets should also be non-build targets.
Unfortunately, vdso_install requires the compiler because it builds
vdso before installation. This is a problem that must be fixed by a
separate patch.

Reported-by: Israel Tsadok <itsadok@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/Makefile b/Makefile
index 80bae8a..d798234 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -264,6 +264,10 @@ no-dot-config-targets := $(clean-targets) \
                         $(version_h) headers headers_% archheaders archscripts \
                         %asm-generic kernelversion %src-pkg dt_binding_check \
                         outputmakefile
+# Installation targets should not require compiler. Unfortunately, vdso_install
+# is an exception where build artifacts may be updated. This must be fixed.
+no-compiler-targets := $(no-dot-config-targets) install dtbs_install \
+                       headers_install modules_install kernelrelease image_name
 no-sync-config-targets := $(no-dot-config-targets) %install kernelrelease \
                          image_name
 single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
@@ -271,6 +275,7 @@ single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
 config-build   :=
 mixed-build    :=
 need-config    := 1
+need-compiler  := 1
 may-sync-config        := 1
 single-build   :=
 
@@ -280,6 +285,12 @@ ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
        endif
 endif
 
+ifneq ($(filter $(no-compiler-targets), $(MAKECMDGOALS)),)
+       ifeq ($(filter-out $(no-compiler-targets), $(MAKECMDGOALS)),)
+               need-compiler :=
+       endif
+endif
+
 ifneq ($(filter $(no-sync-config-targets), $(MAKECMDGOALS)),)
        ifeq ($(filter-out $(no-sync-config-targets), $(MAKECMDGOALS)),)
                may-sync-config :=
@@ -586,7 +597,9 @@ endif
 
 # Include this also for config targets because some architectures need
 # cc-cross-prefix to determine CROSS_COMPILE.
+ifdef need-compiler
 include $(srctree)/scripts/Makefile.compiler
+endif
 
 ifdef config-build
 # ===========================================================================