kbuild: check the minimum compiler version in Kconfig

Paul Gortmaker reported a regression in the GCC version check. [1]
If you use GCC 4.8, the build breaks before showing the error message
"error Sorry, your version of GCC is too old - please use 4.9 or newer."

I do not want to apply his fix-up since it implies we would not be able
to remove any cc-option test. Anyway, I admit checking the GCC version
in <linux/compiler-gcc.h> is too late.

Almost at the same time, Linus also suggested to move the compiler
version error to Kconfig time. [2]

I unified the two similar scripts, gcc-version.sh and clang-version.sh
into cc-version.sh. The old scripts invoked the compiler multiple times
(3 times for gcc-version.sh, 4 times for clang-version.sh). I refactored
the code so the new one invokes the compiler just once, and also tried
my best to use shell-builtin commands where possible.

The new script runs faster.

  $ time ./scripts/clang-version.sh clang
  120000

  real    0m0.029s
  user    0m0.012s
  sys     0m0.021s

  $ time ./scripts/cc-version.sh clang
  Clang 120000

  real    0m0.009s
  user    0m0.006s
  sys     0m0.004s

cc-version.sh also shows an error message if the compiler is too old:

  $ make defconfig CC=clang-9
  *** Default configuration is based on 'x86_64_defconfig'
  ***
  *** Compiler is too old.
  ***   Your Clang version:    9.0.1
  ***   Minimum Clang version: 10.0.1
  ***
  scripts/Kconfig.include:46: Sorry, this compiler is not supported.
  make[1]: *** [scripts/kconfig/Makefile:81: defconfig] Error 1
  make: *** [Makefile:602: defconfig] Error 2

The new script takes care of ICC because we have <linux/compiler-intel.h>
although I am not sure if building the kernel with ICC is well-supported.

[1]: https://lore.kernel.org/r/20210110190807.134996-1-paul.gortmaker@windriver.com
[2]: https://lore.kernel.org/r/CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com

Fixes: 87de84c9140e ("kbuild: remove cc-option test of -Werror=date-time")
Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 29ad68325028..7bcfa24524c2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -26,11 +26,11 @@ config CC_VERSION_TEXT
 	    and then every file will be rebuilt.
 
 config CC_IS_GCC
-	def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
+	def_bool $(success,test "$(cc-name)" = GCC)
 
 config GCC_VERSION
 	int
-	default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
+	default $(cc-version) if CC_IS_GCC
 	default 0
 
 config LD_VERSION
@@ -38,14 +38,15 @@ config LD_VERSION
 	default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
 
 config CC_IS_CLANG
-	def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
+	def_bool $(success,test "$(cc-name)" = Clang)
 
 config LD_IS_LLD
 	def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
 
 config CLANG_VERSION
 	int
-	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
+	default $(cc-version) if CC_IS_CLANG
+	default 0
 
 config LLD_VERSION
 	int