[PATCH 2/3] kbuild: rust: apply `CONFIG_WERROR` to all Rust targets

[Miguel Ojeda <ojeda@kernel.org>]

Make all Rust code (i.e. not just kernel code) respect `CONFIG_WERROR`,
so that we keep everything warning clean.

In particular, this affects targets in `rust/` (`RUSTDOC H`, `RUSTC TL`,
`RUSTDOC T`, `RUSTC T` and `RUSTC P`), plus host programs and any others
we may add later.

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
This one requires the `rusttest` warning cleanup at
https://lore.kernel.org/rust-for-linux/20240519210735.587323-1-ojeda@kernel.org/

 Makefile                   | 4 ++--
 scripts/Makefile.extrawarn | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index fba567a55607..2d0ea441cb9c 100644
--- a/Makefile
+++ b/Makefile
@@ -469,7 +469,7 @@ export rust_common_flags := --edition=2021 \

 KBUILD_HOSTCFLAGS   := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
 KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
-KBUILD_HOSTRUSTFLAGS := $(rust_common_flags) -O -Cstrip=debuginfo \
+KBUILD_HOSTRUSTFLAGS = $(rust_common_flags) -O -Cstrip=debuginfo \
 			-Zallow-features= $(HOSTRUSTFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
@@ -560,7 +560,7 @@ KBUILD_CFLAGS += -fno-PIE
 KBUILD_CFLAGS += -fno-strict-aliasing

 KBUILD_CPPFLAGS := -D__KERNEL__
-KBUILD_RUSTFLAGS := $(rust_common_flags) \
+KBUILD_RUSTFLAGS = $(rust_common_flags) \
 		    -Cpanic=abort -Cembed-bitcode=n -Clto=n \
 		    -Cforce-unwind-tables=n -Ccodegen-units=1 \
 		    -Csymbol-mangling-version=v0 \
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 48114e91c386..990890821889 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -26,8 +26,8 @@ endif

 KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror
 KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y)
-KBUILD_RUSTFLAGS-$(CONFIG_WERROR) += -Dwarnings
-KBUILD_RUSTFLAGS += $(KBUILD_RUSTFLAGS-y)
+rust_common_flags-$(CONFIG_WERROR) += -Dwarnings
+rust_common_flags += $(rust_common_flags-y)

 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds

--
2.45.1