update travis to ubuntu 18.04

just 1 LTS old

contrib/ci/scripts/sanitizer_env.sh

@@ -29,33 +29,8 @@ if [ "X${ASAN_BUILD}" = "X1" ]; then
     ASAN_OPTIONS="${ASAN_OPTIONS},detect_leaks=0" "${@}"
   }
 
-  # Check path to ASan DSO
-  : ${ASAN_DSO?"ASAN_DSO must be specified"}
-  if [ ! -e "${ASAN_DSO}" ]; then
-    echo "ASAN_DSO (${ASAN_DSO}) does not exist"
-    exit 1
-  fi
-  # FIXME: We'll need to refactor this when we can do UBSan builds
-  # against a UBSan DSO.
   function run_non_native_binding() {
-    # We need to preload the ASan DSO that libz3
-    # will have undefined references to.
-    # Don't run leak checking because we get lots reported leaks
-    # in the language runtime (e.g. python).
-    PLATFORM="$(uname -s)"
-    case "${PLATFORM}" in
-      Linux*)
-        LD_PRELOAD="${ASAN_DSO}" run_no_lsan "${@}"
-      ;;
-      Darwin*)
-        DYLD_INSERT_LIBRARIES="${ASAN_DSO}" run_no_lsan "${@}"
-      ;;
-      *)
-        echo "Unknown platform \"${PLATFORM}\""
-        exit 1
-      ;;
-    esac
-    unset PLATFORM
+    "${@}"
   }
 else
   # In non-ASan build just run directly