Add missing file

cmake/ThirdPartyPETSc.cmake

+OPTION(NEKTAR_USE_PETSC
+    "Enable PETSc parallel matrix solver support." OFF)
+
+CMAKE_DEPENDENT_OPTION(THIRDPARTY_BUILD_PETSC
+    "Build PETSc if needed" ON
+    "NEKTAR_USE_PETSC" OFF)
+
+IF( NEKTAR_USE_PETSC )
+    IF (THIRDPARTY_BUILD_PETSC)
+        # TODO
+    ELSE (THIRDPARTY_BUILD_PETSC)
+        INCLUDE (FindPETSc)
+        MESSAGE(STATUS "Found PETSc: ${PETSC_LIBRARIES}")
+    ENDIF (THIRDPARTY_BUILD_PETSC)
+ENDIF( NEKTAR_USE_PETSC )
+
+INCLUDE_DIRECTORIES(${PETSC_INCLUDES})
+
+
+
+
+