export INSTALL_SCLS="devtoolset-4-perftools devtoolset-4-toolchain"
export ENABLE_SCLS=devtoolset-4

export INSTALL_SCLS=devtoolset-4
export INSTALL_PKGS="devtoolset-4-perftools devtoolset-4-toolchain"
export ENABLE_SCLS=devtoolset-4

Use INSTALL_PKGS for picking what should be installed
Use INSTALL_PKGS for picking what should be installed
