Adds an old-kernel-gcc-hdrs bbclass to provide the...

Adds an old-kernel-gcc-hdrs bbclass to provide the include/linux/compiler-gccX.h headers needed by 3.10 kernels when built with newer GCC versions (5, 6 and now 7 with the upgrade to rocko)

classes/old-kernel-gcc-hdrs.bbclass

+#
+# This class is used to create dummy headers for newer versions of GCC not supported by the kernel being compiled
+#
+
+do_configure_prepend() {
+    echo "#include <linux/compiler-gcc4.h>" > ${S}/include/linux/compiler-gcc5.h
+    echo "#include <linux/compiler-gcc5.h>" > ${S}/include/linux/compiler-gcc6.h
+    echo "#include <linux/compiler-gcc6.h>" > ${S}/include/linux/compiler-gcc7.h
+}
+