Fix CMake variable replacement notation

Fix other locations where the CMakeLists.txt files use the "@@" notation
to denote a variable substitution instead of the "${}" notation.

OSEHRA-Id: http://issues.osehra.org/browse/OAT-155
Change-Id: I90e98c5edff3e7c460f6afaf9aa6e1c6a0e882f7
Merge "Fix CMake variable replacement notation"