base: Revert 9277177eccff and use getenv/setenv for UTC time

This patch reverts changeset 9277177eccff which does not do what it
was intended to do. In essence, we go back to implementing mkutctime
much like the non-standard timegm extension.

src/base/time.cc

@@ -150,7 +150,32 @@ sleep(const Time &time)
 time_t
 mkutctime(struct tm *time)
 {
-    time_t local = mktime(time);
-    return mktime(gmtime(&local));
+    // get the current timezone
+    char *tz = getenv("TZ");
+
+    // copy the string as the pointer gets invalidated when updating
+    // the environment
+    if (tz) {
+        tz = strdup(tz);
+        if (!tz) {
+            fatal("Failed to reserve memory for UTC time conversion\n");
+        }
+    }
+
+    // change to UTC and get the time
+    setenv("TZ", "", 1);
+    tzset();
+    time_t ret = mktime(time);
+
+    // restore the timezone again
+    if (tz) {
+        setenv("TZ", tz, 1);
+        free(tz);
+    } else {
+        unsetenv("TZ");
+    }
+    tzset();
+
+    return ret;
 }
 

src/dev/sparc/dtod.cc

@@ -53,8 +53,7 @@ DumbTOD::DumbTOD(const Params *p)
     : BasicPioDevice(p, 0x08)
 {
     struct tm tm = p->time;
-    time_t local = mktime(&tm);
-    todTime = mktime(gmtime(&local));
+    todTime = mkutctime(&tm);
 
     DPRINTFN("Real-time clock set to %s\n", asctime(&tm));
     DPRINTFN("Real-time clock set to %d\n", todTime);