build-sys: use -Og instead of -O0 to catch warnings

  $ touch src/core/dbus.c; make CFLAGS=-O0
  make --no-print-directory all-recursive
  Making all in .
    CC       src/core/libsystemd_core_la-dbus.lo
    CCLD     libsystemd-core.la

  $ touch src/core/dbus.c; make CFLAGS=-Og
  make --no-print-directory all-recursive
  Making all in .
    CC       src/core/libsystemd_core_la-dbus.lo
  src/core/dbus.c: In function 'init_registered_system_bus':
  src/core/dbus.c:798:18: warning: 'id' may be used uninitialized in this function [-Wmaybe-uninitialized]
           dbus_free(id);
                    ^
    CCLD     libsystemd-core.la

-Og Optimize debugging experience. -Og enables optimizations that do
not interfere with debugging. It should be the optimization level of
choice for the standard edit-compile-debug cycle, offering a
reasonable level of optimization while maintaining fast compilation
and a good debugging experience.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index e23847bbea..8051cb36ec 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -465,8 +465,10 @@ static int item_set_perms(Item *i, const char *path) {
 }
 
 static int write_one_file(Item *i, const char *path) {
-        int r, e, fd, flags;
+        int e, flags;
+        int fd = -1;
         struct stat st;
+        int r = 0;
 
         flags = i->type == CREATE_FILE ? O_CREAT|O_APPEND :
                 i->type == TRUNCATE_FILE ? O_CREAT|O_TRUNC : 0;
@@ -638,8 +640,9 @@ static int glob_item(Item *i, int (*action)(Item *, const char *)) {
 }
 
 static int create_item(Item *i) {
-        int r, e;
+        int e;
         struct stat st;
+        int r = 0;
 
         assert(i);