ARM: 8767/1: add support for building ARM kernel with clang

Use cc-options call for compiler options which are not available
in clang. With this patch an ARMv7 multi platform kernel can be
successfully build using clang (tested with version 5.0.1).
Based-on-patches-by: NBehan Webster <behanw@converseincode.com>
Signed-off-by: NStefan Agner <stefan@agner.ch>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>

arch/arm/boot/compressed/Makefile

@@ -113,7 +113,7 @@ CFLAGS_fdt_ro.o := $(nossp_flags)
 CFLAGS_fdt_rw.o := $(nossp_flags)
 CFLAGS_fdt_wip.o := $(nossp_flags)
 
-ccflags-y := -fpic -mno-single-pic-base -fno-builtin -I$(obj)
+ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin -I$(obj)
 asflags-y := -DZIMAGE
 
 # Supply kernel BSS size to the decompressor via a linker symbol.