Support symlinking to dart-sdk executables on Linux and Mac.

sdk/bin/dartanalyzer

 #!/bin/bash --posix
 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 set -e
 
-# Setting SCRIPT_DIR this way is ugly, but is needed to handle the case where
-# dart-sdk/bin has been symlinked to. On MacOS, readlink doesn't work
-# with this case.
-SCRIPT_DIR="$(cd "${0%/*}" ; pwd -P)"
+function follow_links() {
+  file="$1"
+  while [ -h "$file" ]; do
+    # On Mac OS, readlink -f doesn't work.
+    file="$(readlink "$file")"
+  done
+  echo "$file"
+}
+
+# Unlike $0, $BASH_SOURCE points to the absolute path of this file.
+PROG_NAME="$(follow_links "$BASH_SOURCE")"
+
+# Handle the case where dart-sdk/bin has been symlinked to.
+SCRIPT_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
+
 DART_ANALYZER_HOME="$(cd "${SCRIPT_DIR%/*}" ; pwd -P)"
 
 FOUND_BATCH=0
 FOUND_SDK=0
 for ARG in "$@"
 do
   case $ARG in
     -batch|--batch)
       FOUND_BATCH=1
       ;;
@@ skipping 48 matching lines @@
   # On other architectures
   # -batch invocations will do better with a server vm
   # invocations for analyzing a single file do better with a client vm
   if [ $FOUND_BATCH -eq 0 ] ; then
     EXTRA_JVMARGS+=" -client "
   fi
 fi
 
 exec java $EXTRA_JVMARGS $DART_JVMARGS -ea -jar \
   "$DART_ANALYZER_LIBS/dartanalyzer.jar" "${DART_SDK[@]}" $@