toolchain: bump ARC toolchain components to arc-2015.12

This change introduces newer ARC toolchain in Buildroot.

That new arc-2015.12 release doesn't bring any significant changes
but mostly is focused on fixes and minor improvements here and there.
Most noticeable changes are:
 * GCC: Source update to v4.8.5
 * GDB: Updated to upstream 7.10 release.

You may find more info on fixes and improvements in that release at:
https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases/tag/arc-2015.12

Signed-off-by: Lada Trimasova <ltrimas@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gcc/Config.in.host

@@ -114,7 +114,7 @@ config BR2_GCC_VERSION
 	default "4.8.5"     if BR2_GCC_VERSION_4_8_X
 	default "4.9.3"     if BR2_GCC_VERSION_4_9_X
 	default "5.3.0"     if BR2_GCC_VERSION_5_X
-	default "arc-2015.12-rc1" if BR2_GCC_VERSION_4_8_ARC
+	default "arc-2015.12" if BR2_GCC_VERSION_4_8_ARC
 
 config BR2_EXTRA_GCC_CONFIG_OPTIONS
 	string "Additional gcc options"

package/gcc/gcc.hash

@@ -9,4 +9,4 @@ sha512  9ac57377a6975fc7adac704ec81355262b9f537def6955576753b87715470a20ee6a2a31
 # From ftp://gcc.gnu.org/pub/gcc/releases/gcc-5.3.0/sha512.sum
 sha512  d619847383405fd389f5a2d7225f97fedb01f81478dbb8339047ccba7561a5c20045ab500a8744bffd19ea51892ce09fc37f862f2cfcb42de0f0f8cd8f8da37a  gcc-5.3.0.tar.bz2
 # No hash for the ARC variant, comes from the github-helper:
-none  xxx  gcc-arc-2015.12-rc1.tar.gz
+none  xxx  gcc-arc-2015.12.tar.gz