[PATCH] kbuild: show warning for 'make headers_check'

[Masahiro Yamada <masahiroy@kernel.org>]

Since commit 7ecaf069da52 ("kbuild: move headers_check rule to
usr/include/Makefile"), the headers_check target is no-op.

This stub target is remaining here in case some scripts still invoke
'make headers_check'. In order to prompt people to remove stale code,
show a noisy warning message if used. The stub will be really removed
after the Linux 5.15 release.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index f9b54da2fca0..a3336d9b4a22 100644
--- a/Makefile
+++ b/Makefile
@@ -1339,7 +1339,11 @@ headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
 # Deprecated. It is no-op now.
 PHONY += headers_check
 headers_check:
-	@:
+	@echo >&2 "=================== WARNING ==================="
+	@echo >&2 "Since Linux 5.5, 'make headers_check' is no-op,"
+	@echo >&2 "and will be removed after Linux 5.15 release."
+	@echo >&2 "Please remove headers_check from your scripts."
+	@echo >&2 "==============================================="
 
 ifdef CONFIG_HEADERS_INSTALL
 prepare: headers
-- 
2.27.0