riscv: Hoist linker relaxation disabling logic into Kconfig

Certain configurations may need to be disabled if linker relaxation is
in use, such as DWARF5 with ld.lld < 18. Hoist the logic of whether or
not linker relaxation is in use into Kconfig so decisions can be made at
configuration time.

Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20231205-riscv-restrict-dwarf5-llvm-v2-1-aedf00a382ac@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: nathanchance

arch/riscv/Kconfig

@@ -181,6 +181,11 @@ config HAVE_SHADOW_CALL_STACK
 	# https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/a484e843e6eeb51f0cb7b8819e50da6d2444d769
 	depends on $(ld-option,--no-relax-gp)
 
+config RISCV_USE_LINKER_RELAXATION
+	def_bool y
+	# https://github.com/llvm/llvm-project/commit/6611d58f5bbcbec77262d392e2923e1d680f6985
+	depends on !LD_IS_LLD || LLD_VERSION >= 150000
+
 config ARCH_MMAP_RND_BITS_MIN
 	default 18 if 64BIT
 	default 8

arch/riscv/Makefile

@@ -43,16 +43,14 @@ else
 	KBUILD_LDFLAGS += -melf32lriscv
 endif
 
-ifeq ($(CONFIG_LD_IS_LLD),y)
-ifeq ($(call test-lt, $(CONFIG_LLD_VERSION), 150000),y)
+ifndef CONFIG_RISCV_USE_LINKER_RELAXATION
 	KBUILD_CFLAGS += -mno-relax
 	KBUILD_AFLAGS += -mno-relax
 ifndef CONFIG_AS_IS_LLVM
 	KBUILD_CFLAGS += -Wa,-mno-relax
 	KBUILD_AFLAGS += -Wa,-mno-relax
 endif
 endif
-endif
 
 ifeq ($(CONFIG_SHADOW_CALL_STACK),y)
 	KBUILD_LDFLAGS += --no-relax-gp