src: Fix declaration of ldm_new

GCC 15 forbids declaring a function with () instead of (void).
Declaring it properly reveals an actual bug in ldmtool.

ldmtool.c: In function ‘main’:
ldmtool.c:859:23: error: too many arguments to function ‘ldm_new’; expected 0, have 1
  859 |     LDM * const ldm = ldm_new(&err);
      |                       ^~~~~~~ ~~~~
In file included from ldmtool.c:38:
ldm.h:259:6: note: declared here
  259 | LDM *ldm_new();
      |      ^~~~~~~

Author: rwmjones

src/ldm.c

@@ -2354,7 +2354,7 @@ ldm_add_fd(LDM * const o, const int fd, const guint secsize,
 }
 
 LDM *
-ldm_new()
+ldm_new(void)
 {
     LDM *ldm = LDM_CAST(g_object_new(LDM_TYPE, NULL));
     ldm->priv->disk_groups = g_array_sized_new(FALSE, FALSE,

src/ldm.h

@@ -256,7 +256,7 @@ GType ldm_disk_group_get_type(void);
  *
  * Returns: (transfer full): a new #LDM object
  */
-LDM *ldm_new();
+LDM *ldm_new(void);
 
 /**
  * ldm_add:

src/ldmtool.c

@@ -856,7 +856,7 @@ main(int argc, char *argv[])
     g_type_init();
 #endif
 
-    LDM * const ldm = ldm_new(&err);
+    LDM * const ldm = ldm_new();
 
     int ret = 0;