bugfix: use execvp to find mv at runtime, fixes AppImage portability

Using execvp("mv", ...) searches PATH at runtime instead of compiling
in a build-time path, which also fixes the NixOS case without needing
Meson to discover mv.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: andy5995

meson.build

@@ -60,9 +60,6 @@ foreach h : check_headers
   endif
 endforeach
 
-mv_prog = find_program('mv', required: true)
-add_project_arguments('-DMV_PATH="' + mv_prog.full_path() + '"', language: 'c')
-
 localedir = join_paths(get_option('prefix'), get_option('localedir'))
 subdir('po')
 

src/utils.c

@@ -517,16 +517,11 @@ safe_mv_via_exec(const char *src, const char *dst, int *out_errno)
 
   if (pid == 0)
   {
-    /* child: exec mv using path discovered by Meson */
-    char *const argv_mv[] = {
-      MV_PATH,                  /* argv[0] should match the executed path */
-      (char *) src,
-      (char *) dst,
-      NULL
-    };
-
-    execv(MV_PATH, argv_mv);
-    _exit(127);                 /* only reached on execv failure */
+    /* child: exec mv, searching PATH at runtime so this works on
+       non-FHS systems (e.g. NixOS) and in AppImages */
+    char *const argv_mv[] = { "mv", (char *) src, (char *) dst, NULL };
+    execvp("mv", argv_mv);
+    _exit(127);                 /* only reached on execvp failure */
   }