[PATCH v4 3/4] rust: add a Kconfig function to test for support of bindgen options

[Asuna Yang <spriteovo@gmail.com>]

Use the `BINDGEN_EXTRA_CLANG_ARGS` environment variable to pass the
`--target` option for cross compiling, so that the function can be used
to test both bindgen options and bindgen backend options.

Signed-off-by: Asuna Yang <SpriteOvO@gmail.com>
---
 scripts/Kconfig.include | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 33193ca6e803..a8cfe9f408a5 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -75,3 +75,8 @@ rustc-llvm-version := $(shell,$(srctree)/scripts/rustc-llvm-version.sh $(RUSTC))
 # If you are testing for unstable features, consider testing RUSTC_VERSION
 # instead, as features may have different completeness while available.
 rustc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(RUSTC) $(1) --crate-type=rlib /dev/null --out-dir=.tmp_$$ -o .tmp_$$/tmp.rlib)
+
+# $(rust-bindgen-option,<flag>)
+# Return y if the Rust bindgen supports <flag>, n otherwise
+# To test options for the bindgen backend, add -- at the beginning, for example: $(rust-bindgen-option,-- <backend-flag>)
+rust-bindgen-option = $(success,trap "rm -f .tmp_$$.h" EXIT; touch .tmp_$$.h; BINDGEN_EXTRA_CLANG_ARGS+=" --target=$(BINDGEN_TARGET)" $(BINDGEN) .tmp_$$.h $(1))

-- 
2.51.1