erofs-utils: misc: Fix potential memory leak in realloc failure path

erofs-utils: misc: Fix potential memory leak in realloc failure path

As realloc returns NULL on failure, the original value will be
overwritten if it is used as lvalue. Fix this by using a temporary
variable to hold the return value and exit with -ENOMEM in case of
failure. This patch fixes 2 of the realloc blocks with similar fix.

Signed-off-by: Sandeep Dhavale <dhavale@google.com>
Link: https://lore.kernel.org/r/20240718202204.1224620-1-dhavale@google.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>