[PATCH v6 1/2] kbuild: add rustc-lt-version macro

[HeeSu Kim]

Add `rustc-lt-version` macro to `scripts/Makefile.compiler` for version
upper bound checks, mirroring the existing `rustc-min-version`.

Use a non-inclusive (less-than) comparison so that callers can express
clean version boundaries such as `109000` (Rust 1.90.0) rather than
`108999`, which is also easier to remove once the toolchain minimum
version is bumped past the bound.

This will be used to bound workarounds to specific compiler version
ranges.

Originally posted as `rustc-max-version` in v5 [1]; renamed to
`rustc-lt-version` on this respin per Miguel's direction to simplify
the delta and avoid the `99` form [2].

[1] https://lore.kernel.org/rust-for-linux/20260205131522.2942928-1-mlksvender@xxxxxxxxx/
[2] https://lore.kernel.org/rust-for-linux/CANiq72n-z0v_deUVPWeg1h0c6KQ+r6xfNDf72o29_0yy6KbqGA@xxxxxxxxxxxxxx/

Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Link: https://lore.kernel.org/rust-for-linux/CANiq72n39eU9WE=Yh0_yJzmqMxo=QAaU2pN0UqP9jZ7bT7rhgA@xxxxxxxxxxxxxx/
Acked-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Acked-by: Nicolas Schier <nsc@xxxxxxxxxx>
Signed-off-by: HeeSu Kim <mlksvender@xxxxxxxxx>
---
 scripts/Makefile.compiler | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index ef91910de265..fd039e228800 100644
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -71,6 +71,10 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
 # Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
 rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
 
+# rustc-lt-version
+# Usage: rustc-$(call rustc-lt-version, 109000) += -Cfoo
+rustc-lt-version = $(if $(call rustc-min-version,$1),,y)
+
 # ld-option
 # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
 ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
-- 
2.52.0