Allow a QEMU host to set the time and shutdown Guix guests.  Styled
after the patch from the Nix package:

https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/virtualization/qemu/fix-qemu-ga.patch

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -84,6 +84,7 @@ static void ga_wait_child(pid_t pid, int *status, Error **errp)
 void qmp_guest_shutdown(bool has_mode, const char *mode, Error **errp)
 {
     const char *shutdown_flag;
+    const char *command;
     Error *local_err = NULL;
     pid_t pid;
     int status;
@@ -101,10 +102,13 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **errp)
     slog("guest-shutdown called, mode: %s", mode);
     if (!has_mode || strcmp(mode, "powerdown") == 0) {
         shutdown_flag = powerdown_flag;
+        command = "shutdown";
     } else if (strcmp(mode, "halt") == 0) {
         shutdown_flag = halt_flag;
+        command = "halt";
     } else if (strcmp(mode, "reboot") == 0) {
         shutdown_flag = reboot_flag;
+        command = "reboot";
     } else {
         error_setg(errp,
                    "mode is invalid (valid values are: halt|powerdown|reboot");
@@ -123,6 +127,11 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, Error **errp)
         execl("/sbin/shutdown", "shutdown", shutdown_flag, "-g0", "-y",
               "hypervisor initiated shutdown", (char *)NULL);
 #else
+        /* try Guix’s shutdown/halt/reboot first */
+        char *path = g_strdup_printf("/run/current-system/profile/sbin/%s", command);
+        execl(path, command, (char *)NULL);
+        g_free(path);
+
         execl("/sbin/shutdown", "shutdown", "-h", shutdown_flag, "+0",
                "hypervisor initiated shutdown", (char *)NULL);
 #endif
@@ -159,10 +168,12 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
     Error *local_err = NULL;
     struct timeval tv;
     static const char hwclock_path[] = "/sbin/hwclock";
+    static const char hwclock_path_guix[] = "/run/current-system/profile/sbin/hwclock";
     static int hwclock_available = -1;
 
     if (hwclock_available < 0) {
-        hwclock_available = (access(hwclock_path, X_OK) == 0);
+        hwclock_available = (access(hwclock_path_guix, X_OK) == 0) ||
+                            (access(hwclock_path, X_OK) == 0);
     }
 
     if (!hwclock_available) {
@@ -208,6 +219,8 @@ void qmp_guest_set_time(bool has_time, int64_t time_ns, Error **errp)
 
         /* Use '/sbin/hwclock -w' to set RTC from the system time,
          * or '/sbin/hwclock -s' to set the system time from RTC. */
+        execl(hwclock_path_guix, "hwclock", has_time ? "-w" : "-s",
+               NULL);
         execl(hwclock_path, "hwclock", has_time ? "-w" : "-s", NULL);
         _exit(EXIT_FAILURE);
     } else if (pid < 0) {
es.</a><span class='msg-avail'>...<span class='msg-tooltip'>Remove .gitignore entries where they match source files that are tracked in
Git.  This is relevant to me at least, as some code searching tools use
.gitignore files and will ignore matched files.
</span></span></td><td>Christopher Baines</td></tr>