avr-gcc-4.5.0: command not found

Have You tried accessing the binary with the full path?

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/avr-gcc-4.5.0 - from package: avr-gcc

You may install the required package with command yum install {package}
Error in other languages:
avr-gcc-4.5.0: bevel nie gevind nie
avr-gcc-4.5.0: comandă negăsită
avr-gcc-4.5.0: comando não encontrado
avr-gcc-4.5.0: commande introuvable
avr-gcc-4.5.0: command not found
avr-gcc-4.5.0: käsku ei ole
avr-gcc-4.5.0: không tìm thấy lệnh
avr-gcc-4.5.0: komanda nerasta
avr-gcc-4.5.0: Kommando nicht gefunden.
avr-gcc-4.5.0: kommandot finns inte
avr-gcc-4.5.0: komut yok
avr-gcc-4.5.0: nie znaleziono polecenia
avr-gcc-4.5.0: níor aimsíodh an t-ordú
avr-gcc-4.5.0: no se encontró la orden
avr-gcc-4.5.0: no s'ha trobat l'ordre
avr-gcc-4.5.0: opdracht niet gevonden
avr-gcc-4.5.0: parancs nem található
avr-gcc-4.5.0: perintah tidak ditemukan
avr-gcc-4.5.0: príkaz nenájdený
avr-gcc-4.5.0: příkaz nenalezen
avr-gcc-4.5.0: команда не найдена
avr-gcc-4.5.0: командата не е открита
avr-gcc-4.5.0: 命令找不到
avr-gcc-4.5.0: コマンドが見つかりません