Fix dmesg -c error output.
Use perror_exit to show the likely "Operation not permitted" if klogctl fails.
diff --git a/toys/lsb/dmesg.c b/toys/lsb/dmesg.c
index aac638d..d608446 100644
--- a/toys/lsb/dmesg.c
+++ b/toys/lsb/dmesg.c
@@ -45,7 +45,7 @@
if (!size && 1>(size = klogctl(10, 0, 0))) perror_exit("klogctl");;
data = to = from = xmalloc(size+1);
size = klogctl(3 + (toys.optflags & FLAG_c), data, size);
- if (size < 0) error_exit("klogctl");
+ if (size < 0) perror_exit("klogctl");
data[size] = 0;
// Filter out level markers and optionally time markers