Tester may have set LD_LIBRARY_PATH to find libraries required
by notmuch. Therefore add $TEST_DIRECTORY/../lib to the beginning
of current list of library paths in $LD_LIBRARY_PATH before running
symbol-test.
 . ./test-lib.sh
 
 run_test(){
-    result=$(LD_LIBRARY_PATH=$TEST_DIRECTORY/../lib $TEST_DIRECTORY/symbol-test 2>&1)
+    result=$(LD_LIBRARY_PATH="$TEST_DIRECTORY/../lib${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}" $TEST_DIRECTORY/symbol-test 2>&1)
 }
 
 output="A Xapian exception occurred opening database: Couldn't stat 'fakedb/.notmuch/xapian'