fix(cros-kernel2.eclass): Don't install invalid source/build symlinks.

If the kernel sources aren't installed there is no point to installing
these symlinks.

sdk_container/src/third_party/coreos-overlay/eclass/cros-kernel2.eclass

@@ -146,6 +146,9 @@ cros-kernel2_src_install() {
 
 	if use source; then
 		install_kernel_sources
+	else
+		# Remove invalid symlinks when source isn't installed
+		rm -f "${D}/lib/modules/${version}/"{build,source}
 	fi
 }