PR build Trilinos_pullrequest_gcc_4.9.3_SERIAL and the nightly "Clean" build Linux-gcc-4.9.3-SERIAL_Release_gcc_4.9.3__DEV are not the same

Created by: bartlettroscoe

CC: @dridzal, @crtrott, @srajama1

@trilinos/framework,

It looks like the PR build Trilinos_pullrequest_gcc_4.9.3_SERIAL and the nightly "Clean" build Linux-gcc-4.9.3-SERIAL_Release_gcc_4.9.3__DEV are NOT the same!

The configuration for the PR build Trilinos_pullrequest_gcc_4.9.3_SERIAL for this PR shown here shows the Pthread TPL being explicitly enabled:

Explicitly enabled TPLs on input (by user):  Pthread BLAS LAPACK Boost Zlib HDF5 Netcdf SuperLU BoostLib DLlib 10
...
Final set of enabled TPLs:  Pthread BLAS LAPACK Boost Zlib HDF5 Netcdf SuperLU BoostLib DLlib 10

but the nightly "Clean" build Linux-gcc-4.9.3-SERIAL_Release_gcc_4.9.3__DEV shown here shows that the Pthread is not being explicitly enabled:

Explicitly enabled TPLs on input (by user):  BLAS LAPACK Boost Zlib HDF5 Netcdf SuperLU BoostLib DLlib 9
...
Final set of enabled TPLs:  BLAS LAPACK Boost Zlib HDF5 Netcdf SuperLU BoostLib X11 DLlib 10

This explains how code got onto 'develop' that was allowed to break the "Clean" non-MPI SERIAL build (see #3773 (closed) and #3803)

I thought the goal of the adding a (non-MPI) SERIAL PR build was to guarantee that the nightly "Clean" SERIAL would be clean?