build_firefox: 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/build_firefox - from package: translate-toolkit

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

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