hwclock: fix sizeof bug (used it on pointer, not array); make --systohc exact

function                                             old     new   delta
hwclock_main                                         329     428     +99
rtc_adjtime_is_utc                                   138     134      -4
edir                                                 365     354     -11
read_rtc                                              39      23     -16
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 99/-31)             Total: 68 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/runit/chpst.c b/runit/chpst.c
index 082d726..1a68eb7 100644
--- a/runit/chpst.c
+++ b/runit/chpst.c
@@ -104,7 +104,7 @@
 	xchdir(directory_name);
 	dir = xopendir(".");
 	for (;;) {
-		RESERVE_CONFIG_BUFFER(buf, 256);
+		char buf[256];
 		char *tail;
 		int size;
 
@@ -148,7 +148,6 @@
 				break;
 		}
 		xsetenv(d->d_name, buf);
-		RELEASE_CONFIG_BUFFER(buf);
 	}
 	closedir(dir);
 	if (fchdir(wdir) == -1)