gnatlink: 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 CentOS possible default full paths are:

/usr/bin/gnatlink - from package: gcc-gnat

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/gnatlink - from package: gnat-4.9

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

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