arch/Config.in.arc: fix BR2_READELF_ARCH_NAME

On ARC, depending on the CPU selected, the ELF machine number might be
different. Take this into account when defining BR2_READELF_ARCH_NAME.

Fixes:

   http://autobuild.buildroot.net/results/0a1957056e07cedc4839439c0ea8ebd1f646b904/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

arch/Config.in.arc

@@ -39,7 +39,8 @@ config BR2_GCC_TARGET_CPU
 	default "archs"	 if BR2_archs38
 
 config BR2_READELF_ARCH_NAME
-	default "ARCv2"
+	default "ARCompact" 	if BR2_arc750d || BR2_arc770d
+	default "ARCv2"		if BR2_archs38
 
 choice
 	prompt "MMU Page Size"