我正在尝试使用以下命令在 openwrt 上安装 gcc：
opkg install gcc
但它给了我以下错误：
/bin/ash: gcc: not found
root@OpenWrt:/mp1# opkg install gcc
Unknown package 'gcc'.
Collected errors:
* opkg_install_cmd: Cannot install package gcc.
我尝试使用更新 opkg opkg update，但得到以下信息：
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packagez
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packageo
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packaget
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/generic/packages
wget: bad address 'downloads.openwrt.org'
Signature check failed.
Remove wrong Signature file.
Collected errors:
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/b
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/0
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/c
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/u
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
* opkg_download: Failed to download http://downloads.openwrt.org/chaos_calmer/1
我该如何解决？