WORKSPACE: Add gtest.
WORKSPACE: Add gtest.

Fixes C++ tests in gapil/runtime

google/gapid,Qining/gapid,Qining/gapid,pmuetschard/gapid,pmuetschard/gapid,Qining/gapid,Qining/gapid,baldwinn860/gapid,baldwinn860/gapid,Qining/gapid,Qining/gapid,baldwinn860/gapid,google/agi,google/agi,pmuetschard/gapid,pmuetschard/gapid,google/agi,baldwinn860/gapid,Qining/gapid,google/gapid,pmuetschard/gapid,google/gapid,google/gapid,baldwinn860/gapid,google/gapid,google/agi,baldwinn860/gapid,google/gapid,Qining/gapid,pmuetschard/gapid,google/agi,pmuetschard/gapid,pmuetschard/gapid,google/gapid,google/agi,baldwinn860/gapid,google/agi,google/agi,google/gapid,baldwinn860/gapid