Add a new line to the end of the generated main.cxx for the hpux compiler.

Some HPUX compilers give this error: Error 690: "/home/cport/Dashboards/My Tests/CMake-build/Tests/CheckCompilerRelatedVariables/main.cxx", line 1 # Nonempty source files must end with a newline that is not preceded by a backslash.

Tests/CheckCompilerRelatedVariables/CMakeLists.txt

@@ -76,7 +76,8 @@ endif()
 
 file(WRITE
   "${CMAKE_CURRENT_BINARY_DIR}/main.cxx"
-  "int main() { return 0; }"
+  "int main() { return 0; }
+"
   )
 
 add_executable(