Set custom AR_ for each class

TEST=Booted Nyan Blaze
BUG=none
BRANCH=none
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

Original-Change-Id: I7e822e16117240f732ac55bb2c3816486a3e10cc
Original-Reviewed-on: https://chromium-review.googlesource.com/204870
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Original-Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>
(cherry picked from commit 967455d6fed014f82198de4987ec103bb7c33d25)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I88025887fb0134f1e75028e0a4ed0c78af281c96
Reviewed-on: http://review.coreboot.org/8143
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/toolchain.inc b/toolchain.inc
index e6f530a..b54d959 100644
--- a/toolchain.inc
+++ b/toolchain.inc
@@ -87,6 +87,7 @@
 CC_$(1) := $(CC_$(2))
 LD_$(1) := $(LD_$(2))
 NM_$(1) := $(NM_$(2))
+AR_$(1) := $(AR_$(2))
 OBJCOPY_$(1) := $(OBJCOPY_$(2))
 OBJDUMP_$(1) := $(OBJDUMP_$(2))
 STRIP_$(1) := $(STRIP_$(2))