rust: kbuild: support -Cjump-tables=n for Rust 1.93.0

Rust 1.93.0 (expected 2026-01-22) is stabilizing `-Zno-jump-tables`
[1][2] as `-Cjump-tables=n` [3].

Without this change, one would eventually see:

      RUSTC L rust/core.o
    error: unknown unstable option: `no-jump-tables`

Thus support the upcoming version.

Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Link: rust-lang/rust#116592 [1]
Link: rust-lang/rust#105812 [2]
Link: rust-lang/rust#145974 [3]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251101094011.1024534-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

arch/loongarch/Makefile

@@ -109,7 +109,7 @@ endif
 ifdef CONFIG_RUSTC_HAS_ANNOTATE_TABLEJUMP
 KBUILD_RUSTFLAGS		+= -Cllvm-args=--loongarch-annotate-tablejump
 else
-KBUILD_RUSTFLAGS		+= -Zno-jump-tables # keep compatibility with older compilers
+KBUILD_RUSTFLAGS		+= $(if $(call rustc-min-version,109300),-Cjump-tables=n,-Zno-jump-tables) # keep compatibility with older compilers
 endif
 ifdef CONFIG_LTO_CLANG
 # The annotate-tablejump option can not be passed to LLVM backend when LTO is enabled.

arch/x86/Makefile

@@ -98,7 +98,7 @@ ifeq ($(CONFIG_X86_KERNEL_IBT),y)
 #   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816
 #
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=branch -fno-jump-tables)
-KBUILD_RUSTFLAGS += -Zcf-protection=branch -Zno-jump-tables
+KBUILD_RUSTFLAGS += -Zcf-protection=branch $(if $(call rustc-min-version,109300),-Cjump-tables=n,-Zno-jump-tables)
 else
 KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
 endif