Improve showing build log failure on Travis/Jenkins

[pramodskumbhar]

Currently we are doing:

    # install package
    (spack install -v $package; exit 0)

    # check if package installed properly
    if [[ `spack find $package` == *"No package matches"* ]];  then

        echo " == > PACKAGE INSTALLATION CHECK FAILED, BUILD LOG : "
        cat `spack location $package`/spack-build.out
        exit 1

    fi

But if are installing dependency and that is failed then location is not created yet.

• for NEURON repo it's fine because there are no dependency
• but neuron +profile cause the issue of tau fails

[pramodskumbhar]

Spack now has --show-log-on-error option for install. Fixed upstream.