BUG#12549572 : CMake file does not include gcov option

This patch inserts an 'ENABLE_GCOV' option for enabling gcov compilation
on Linux machines. It modifies the CMakeLists.txt setting this option
to 'OFF' by default.

Note: The option requires a debug build. For example, 
      -DCMAKE_BUILD_TYPE:string="Debug"

CMakeLists.txt

@@ -172,6 +172,13 @@ IF(ENABLE_DEBUG_SYNC)
   SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC") 
 ENDIF() 
  
+OPTION(ENABLE_GCOV "Enable gcov (debug, Linux builds only)" OFF)
+IF (ENABLE_GCOV AND NOT WIN32 AND NOT APPLE)
+  SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -fprofile-arcs -ftest-coverage")
+  SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -fprofile-arcs -ftest-coverage")
+  SET(CMAKE_EXE_LINKER_FLAGS_DEBUG "${CMAKE_EXE_LINKER_FLAGS_DEBUG} -fprofile-arcs -ftest-coverage -lgcov")
+ENDIF()
+
 OPTION(ENABLED_LOCAL_INFILE
  "If we should should enable LOAD DATA LOCAL by default" ${IF_WIN})
 MARK_AS_ADVANCED(ENABLED_LOCAL_INFILE)