[PATCH v2] kbuild: fix linux-headers package build when $(CC) cannot link userspace

[Masahiro Yamada]

Since commit 5f73e7d0386d ("kbuild: refactor cross-compiling
linux-headers package"), the linux-headers Debian package fails to
build when $(CC) cannot build userspace applications, for example,
when using toolchains installed by the 0day bot.

The host programs in the linux-headers package should be rebuilt using
the disto's cross-compiler, ${DEB_HOST_GNU_TYPE}-gcc instead of $(CC).
Hence, the variable 'CC' must be expanded in this shell script instead
of in the top-level Makefile.

Commit f354fc88a72a ("kbuild: install-extmod-build: add missing
quotation marks for CC variable") was not a correct fix because
CC="ccache gcc" should be unrelated when rebuilding userspace tools.

Fixes: 5f73e7d0386d ("kbuild: refactor cross-compiling linux-headers package")
Reported-by: Jeff Johnson <jeff.johnson@xxxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/linux-kbuild/CAK7LNARb3xO3ptBWOMpwKcyf3=zkfhMey5H2KnB1dOmUwM79dA@xxxxxxxxxxxxxx/T/#t
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

Changes in v2:
 - Fix the comment line because 'CC' needs expanding in this script

 scripts/package/install-extmod-build | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/package/install-extmod-build b/scripts/package/install-extmod-build
index b724626ea0ca..2966473b4660 100755
--- a/scripts/package/install-extmod-build
+++ b/scripts/package/install-extmod-build
@@ -62,8 +62,8 @@ if [ "${CC}" != "${HOSTCC}" ]; then
 	#
 	# Clear VPATH and srcroot because the source files reside in the output
 	# directory.
-	# shellcheck disable=SC2016 # $(MAKE), $(CC), and $(build) will be expanded by Make
-	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC="$(CC)" VPATH= srcroot=. $(build)='"${destdir}"/scripts
+	# shellcheck disable=SC2016 # $(MAKE) and $(build) will be expanded by Make
+	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC='"${CC}"' VPATH= srcroot=. $(build)='"${destdir}"/scripts
 
 	rm -f "${destdir}/scripts/Kbuild"
 fi
-- 
2.43.0