Simplify the definition of cmd_hdrtest by moving some of it to a new
variable. This will both enable the upcoming reuse of those flags
and also the extension of cmd_hdrtest.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
---
 usr/include/Makefile | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/usr/include/Makefile b/usr/include/Makefile
index 845d06b63c2b..0b1c9a4b0477 100644
--- a/usr/include/Makefile
+++ b/usr/include/Makefile
@@ -140,11 +140,13 @@ always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/
 target-libc = $(filter $(uses-libc), $*.h)
 target-can-compile = $(filter-out $(no-header-test), $*.h)
 
+hdrtest-flags = -fsyntax-only -Werror \
+		-nostdinc $(if $(target-libc), -I $(srctree)/usr/dummy-include)
+
 # Include the header twice to detect missing include guard.
 quiet_cmd_hdrtest = HDRTEST $<
       cmd_hdrtest = \
-		$(CC) $(c_flags) -fsyntax-only -Werror -x c /dev/null \
-			-nostdinc $(if $(target-libc), -I $(srctree)/usr/dummy-include) \
+		$(CC) $(c_flags) $(hdrtest-flags) -x c /dev/null \
 			$(if $(target-can-compile), -include $< -include $<); \
 		$(PERL) $(src)/headers_check.pl $(obj) $<; \
 		touch $@

-- 
2.53.0