riscv: disable generation of unwind tables

GCC 13 will enable -fasynchronous-unwind-tables by default on riscv.  In
the kernel, we don't have any use for unwind tables yet, so disable them.
More importantly, the .eh_frame section brings relocations
(R_RISC_32_PCREL, R_RISCV_SET{6,8,16}, R_RISCV_SUB{6,8,16}) into modules
that we are not prepared to handle.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Link: https://lore.kernel.org/r/mvmzg9xybqu.fsf@suse.de
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Makefile

@@ -80,6 +80,9 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
         KBUILD_CFLAGS += -fno-omit-frame-pointer
 endif
 
+# Avoid generating .eh_frame sections.
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+
 KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
 KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)