base: linux-lmp: build with clang

meta-lmp-base/recipes-kernel/linux/linux-lmp-clang.inc

@@ -0,0 +1,36 @@
+# https://github.com/kraj/meta-clang#kernel-build-with-clang
+
+TOOLCHAIN:forcevariable = "clang"
+
+DEPENDS:append:toolchain-clang = " clang-cross-${TARGET_ARCH}"
+
+# https://github.com/kraj/meta-clang/issues/856
+KERNEL_CC:remove:toolchain-clang = "-fuse-ld=bfd"
+
+# FIXME: hacks
+do_kernel_configcheck[noexec] = "1"
+
+# error: taking address of packed member 'xxx' of class or structure 'yyy' may result in an unaligned pointer value [-Werror,-Waddress-of-packed-member]
+# because kernel don't use CFLAGS we need to pass it over EXTRA_OEMAKE
+EXTRA_OEMAKE += 'CFLAGS="-Wno-address-of-packed-member"'
+
+# explicitly enable LLVM
+# https://docs.kernel.org/kbuild/llvm.html
+KERNEL_EXTRA_ARGS += "LLVM=1"
+
+# verbose build
+#KERNEL_EXTRA_ARGS += "V=1"
+
+# disable pararel make
+#PARALLEL_MAKE = "-j1"
+
+python __anonymous() {
+    kernel_vars = [
+        ['KERNEL_CC', 'gcc', 'clang'],
+        ['KERNEL_LD', 'ld.bfd', 'ld.lld'],
+        ['KERNEL_AR', 'ar', 'llvm-ar'],
+    ]
+    for [var, match, rep] in kernel_vars:
+        v = d.getVar(var, False)
+        d.setVar(var , v.replace('${HOST_PREFIX}%s' % match, '${HOST_PREFIX}%s' % rep))
+}

meta-lmp-base/recipes-kernel/linux/linux-lmp.inc

@@ -26,3 +26,5 @@ do_deploy:append() {
     cp -a ${B}/.config ${DEPLOYDIR}/${KERNEL_CONFIG_NAME}
     ln -sf ${KERNEL_CONFIG_NAME} ${DEPLOYDIR}/${KERNEL_CONFIG_LINK_NAME}
 }
+
+require linux-lmp-clang.inc