The simplest way to obtain the source files of QMCkl_dgemm is to download a source distribution. This particular repository is for maintainers, who write custom kernels.
./autogen.sh
./configure --enable-mkl CC=icc FC=ifort
make
make check
./autogen.sh
./configure --enable-blas CC=gcc FC=gfortran
make
make check
make install
./autogen.sh
./configure --enable-blas CC=gcc FC=gfortran --enable-fortran
make
make check
make install