os-posix: cleanup: Replace perror with error_report

perror() is defined to fprintf(stderr,...).  HACKING says
fprintf(stderr,...) is wrong.  So perror() is too.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Daniel P. Berrange <berrange@redhat.com>
CC: Michael Tokarev <mjt@tls.msk.ru>
CC: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

os-posix.c

@@ -125,7 +125,7 @@ void os_set_proc_name(const char *s)
     /* Could rewrite argv[0] too, but that's a bit more complicated.
        This simple way is enough for `top'. */
     if (prctl(PR_SET_NAME, name)) {
-        perror("unable to change process name");
+        error_report("unable to change process name: %s", strerror(errno));
         exit(1);
     }
 #else
@@ -247,7 +247,7 @@ static void change_root(void)
             exit(1);
         }
         if (chdir("/")) {
-            perror("not able to chdir to /");
+            error_report("not able to chdir to /: %s", strerror(errno));
             exit(1);
         }
     }
@@ -309,7 +309,7 @@ void os_setup_post(void)
 
     if (daemonize) {
         if (chdir("/")) {
-            perror("not able to chdir to /");
+            error_report("not able to chdir to /: %s", strerror(errno));
             exit(1);
         }
         TFR(fd = qemu_open("/dev/null", O_RDWR));
@@ -383,7 +383,7 @@ int os_mlock(void)
 
     ret = mlockall(MCL_CURRENT | MCL_FUTURE);
     if (ret < 0) {
-        perror("mlockall");
+        error_report("mlockall: %s", strerror(errno));
     }
 
     return ret;