mipsel-linux-gnu-as: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/mipsel-linux-gnu-as - from package: binutils-mipsel-linux-gnu

You may install the required package with command apt-get install {package}

Error in other languages:
mipsel-linux-gnu-as: bevel nie gevind nie
mipsel-linux-gnu-as: comandă negăsită
mipsel-linux-gnu-as: comando não encontrado
mipsel-linux-gnu-as: commande introuvable
mipsel-linux-gnu-as: command not found
mipsel-linux-gnu-as: käsku ei ole
mipsel-linux-gnu-as: không tìm thấy lệnh
mipsel-linux-gnu-as: komanda nerasta
mipsel-linux-gnu-as: Kommando nicht gefunden.
mipsel-linux-gnu-as: kommandot finns inte
mipsel-linux-gnu-as: komut yok
mipsel-linux-gnu-as: nie znaleziono polecenia
mipsel-linux-gnu-as: níor aimsíodh an t-ordú
mipsel-linux-gnu-as: no se encontró la orden
mipsel-linux-gnu-as: no s'ha trobat l'ordre
mipsel-linux-gnu-as: opdracht niet gevonden
mipsel-linux-gnu-as: parancs nem található
mipsel-linux-gnu-as: perintah tidak ditemukan
mipsel-linux-gnu-as: príkaz nenájdený
mipsel-linux-gnu-as: příkaz nenalezen
mipsel-linux-gnu-as: команда не найдена
mipsel-linux-gnu-as: командата не е открита
mipsel-linux-gnu-as: 命令找不到
mipsel-linux-gnu-as: コマンドが見つかりません