The new base docker image sets the LD_LIBRARY_PATH to /usr/local/lib
and the yum is not compatible with the special CURL version we build.
This change fixes that by clearing the LD_LIBRARY_PATH for the yum
command invocation.
Replace the base image with an updated one that now contains
clang 3.9 with PGO support and also the new git. So we don't
need to build it here anymore.