mkfs-util: propagate SOURCE_DATE_EPOCH to mcopy

Co-authored-by: Paul Meyer <49727155+katexochen@users.noreply.github.com>

src/shared/mkfs-util.c

@@ -161,7 +161,7 @@ static int do_mcopy(const char *node, const char *root) {
         if (r == 0) {
                 /* Avoid failures caused by mismatch in expectations between mkfs.vfat and mcopy by disabling
                  * the stricter mcopy checks using MTOOLS_SKIP_CHECK. */
-                execve(mcopy, argv, STRV_MAKE("MTOOLS_SKIP_CHECK=1"));
+                execve(mcopy, argv, STRV_MAKE("MTOOLS_SKIP_CHECK=1", strv_find_prefix(environ, "SOURCE_DATE_EPOCH=")));
 
                 log_error_errno(errno, "Failed to execute mcopy: %m");