meta-zephyr: add support for cortexm3 toolchain

Cortex-M3 is not supported natively by oe-embedded, so we need to
do it here. With these changes it should be possible to run:

To build all Zephyr tests:
    $ MACHINE=qemuarm bitbake zephyr-kernel-test-all
    $ MACHINE=qemuarm bitbake zephyr-kernel-test-all -ctestimage

To build "philosophers" sample:
    $ MACHINE=qemuarm bitbake zephyr-philosophers

Once built, you can run the created "philosophers" image in qemu
(at this point the various paths have to be entered manually):

    $ ./tmp/sysroots/x86_64-linux/usr/bin/qemu-system-arm \
          -kernel ./tmp/deploy/images/qemuarm/philosophers.elf \
          -cpu cortex-m3 -machine lm3s6965evb -nographic -vga none

Signed-off-by: Juro Bystricky <juro.bystricky@intel.com>

conf/distro/machine/include/tune-cortexm3.inc

@@ -0,0 +1,20 @@
+DEFAULTTUNE ?= "cortexm3"
+
+#require conf/machine/include/arm/arch-armv7a.inc
+
+TUNEVALID[cortexm3] = "Enable Cortex-M3 specific processor optimizations"
+TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'cortexm3', ' -mcpu=cortex-m3', '', d)}"
+AVAILTUNES += "cortexm3"
+
+TUNEVALID[armv7m] = "Enable Cortex-M3 specific processor optimizations"
+TUNE_CCARGS .= "${@bb.utils.contains('TUNE_FEATURES', 'armv7m', ' -march=armv7-m', '', d)}"
+MACHINEOVERRIDES =. "${@bb.utils.contains('TUNE_FEATURES', 'armv7m', 'armv7m:', '' ,d)}"
+
+TUNE_PKGARCH_tune-cortexm3 = "cortexm3"
+
+ARMPKGARCH_tune-cortexm3 = "armv7m"
+PACKAGE_EXTRA_ARCHS_tune-cortexm3 ="cortexm3"
+
+TUNE_FEATURES_tune-cortexm3 = "armv7m vfp cortexm3"
+PACKAGE_EXTRA_ARCHS_tune-cortexm3 = "${PACKAGE_EXTRA_ARCHS_tune-armv7at} armv7m-vfp"
+

conf/distro/zephyr.conf

@@ -1,4 +1,5 @@
 require conf/distro/poky.conf
+require conf/distro/machine/include/tune-cortexm3.inc
 
 DISTRO = "zephyr"
 DISTRO_NAME = "Zephyr"
@@ -7,3 +8,4 @@ TCLIBC = "baremetal"
 
 TEST_TARGET = "QemuTargetZephyr"
 TEST_SUITES = "zephyr"
+DEFAULTTUNE_arm ?= "cortexm3"

recipes-devtools/gcc/gcc-cross_6.%.bbappend

@@ -0,0 +1 @@
+EXTRA_OECONF_append_armv7m = " --with-arch=armv7-m --with-mode=thumb "