Format error messages properly

Make use of strerror(errno) and format all errors equally:
function ['parameters']: error message

components/kernel_release.c

@@ -1,6 +1,8 @@
 /* See LICENSE file for copyright and license details. */
+#include <errno.h>
 #include <sys/utsname.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "../util.h"
 
@@ -10,6 +12,7 @@ kernel_release(void)
 	struct utsname udata;
 
 	if (uname(&udata) < 0) {
+		fprintf(stderr, "uname: %s\n", strerror(errno));
 		return NULL;
 	}