icu-config: 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/icu-config - from package: libicu-devel

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

On Debian possible default full paths are:

/usr/bin/icu-config - from package: icu-devtools

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

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