Fix coverage script

Author: igorcanadi

coverage/coverage_test.sh

@@ -11,8 +11,8 @@ fi
 ROOT=".."
 # Fetch right version of gcov
 if [ -d /mnt/gvfs/third-party -a -z "$CXX" ]; then
-  source $ROOT/build_tools/fbcode.gcc471.sh
-  GCOV=$TOOLCHAIN_EXECUTABLES/gcc/gcc-4.7.1/cc6c9dc/bin/gcov
+  source $ROOT/build_tools/fbcode_config.sh
+  GCOV=$GCC_BASE/bin/gcov
 else
   GCOV=$(which gcov)
 fi