csky: Select ARCH_WANT_FRAME_POINTERS only if compiler supports it

Compiling csky:allmodconfig with an upstream C compiler results
in the following error.

csky-linux-gcc: error:
	unrecognized command-line option '-mbacktrace';
	did you mean '-fbacktrace'?

Select ARCH_WANT_FRAME_POINTERS only if gcc supports it to
avoid the error.
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NGuo Ren <guoren@kernel.org>

arch/csky/Kconfig

@@ -8,7 +8,7 @@ config CSKY
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_QUEUED_RWLOCKS
-	select ARCH_WANT_FRAME_POINTERS if !CPU_CK610
+	select ARCH_WANT_FRAME_POINTERS if !CPU_CK610 && $(cc-option,-mbacktrace)
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	select COMMON_CLK
 	select CLKSRC_MMIO