Revert "FROMLIST: rust: add flags for shadow call stack sanitizer"

This reverts commit 263770649d.

A newer version of this patchset will land in 6.12-rc1. Revert the old
version now to avoid merge conflicts in the 6.12-rc1 merge.

Removing these flags could result in miscompilation in Rust+SCS builds,
however commit f126745da8 ("rust: SHADOW_CALL_STACK is incompatible
with Rust") has already landed through 6.11-rc2, so such builds are
rejected by Kconfig.

Change-Id: Id0ea2372811159c67c1afd7e4fed525848c21f8b
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Makefile

@@ -948,7 +948,6 @@ ifdef CONFIG_SHADOW_CALL_STACK
 ifndef CONFIG_DYNAMIC_SCS
 CC_FLAGS_SCS	:= -fsanitize=shadow-call-stack
 KBUILD_CFLAGS	+= $(CC_FLAGS_SCS)
-KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack
 endif
 export CC_FLAGS_SCS
 endif

arch/arm64/Makefile

@@ -57,12 +57,9 @@ KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
 ifneq ($(CONFIG_UNWIND_TABLES),y)
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables -fno-unwind-tables
 KBUILD_AFLAGS	+= -fno-asynchronous-unwind-tables -fno-unwind-tables
-KBUILD_RUSTFLAGS += -Cforce-unwind-tables=n
 else
 KBUILD_CFLAGS	+= -fasynchronous-unwind-tables
 KBUILD_AFLAGS	+= -fasynchronous-unwind-tables
-# TODO: Pass -Zuse-sync-unwind=n once we upgrade to Rust 1.77.0
-KBUILD_RUSTFLAGS += -Cforce-unwind-tables=y
 endif
 
 ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
@@ -117,7 +114,6 @@ endif
 
 ifeq ($(CONFIG_SHADOW_CALL_STACK), y)
 KBUILD_CFLAGS	+= -ffixed-x18
-KBUILD_RUSTFLAGS += -Ctarget-feature=+reserve-x18
 endif
 
 ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)