scarlet: switch to coreboot-sdk

Can't get /usr/bin/arm-none-eabi- working all that well in the chroot:

.../arch/arm/core/aarch32/fatal.c: In function 'arch_syscall_oops':
.../arch/arm/core/aarch32/fatal.c:92:2: warning: missing braces
         around initializer [-Wmissing-braces]
  z_arch_esf_t oops_esf = { 0 };
  ^
.../arch/arm/core/aarch32/fatal.c:92:2: warning: (near initialization
         for 'oops_esf.basic') [-Wmissing-braces]

Coreboot SDK appears to be a newer version of GCC that works fine for
scarlet. Let's switch to that for now until we get the Zephyr SDK
setup.

BUG=b:162531474
TEST=compiles

Change-Id: I681781210848454fa5649c897b3cf23af8250a18
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/zephyr-chrome/+/2332974
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/projects/experimental/scarlet/CMakeLists.txt b/projects/experimental/scarlet/CMakeLists.txt
index 1bb111f..2f3fa19 100644
--- a/projects/experimental/scarlet/CMakeLists.txt
+++ b/projects/experimental/scarlet/CMakeLists.txt
@@ -9,7 +9,7 @@
 
 # Set the compiler needed for this board
 # TODO(b/161461212): move absolute path into another file
-set(CROSS_COMPILE /usr/bin/arm-none-eabi-)
+set(CROSS_COMPILE /opt/coreboot-sdk/bin/arm-eabi-)
 
 find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(scarlet)