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

sdk/bin/dartanalyzer

Index: sdk/bin/dartanalyzer
diff --git a/sdk/bin/dartanalyzer b/sdk/bin/dartanalyzer
index 8a6a072ca990649348c1bd8c5a5317540a8eafc6..740332f2ebee679a2a32022793a4664d082d36b3 100755
--- a/sdk/bin/dartanalyzer
+++ b/sdk/bin/dartanalyzer
@@ -5,10 +5,21 @@
 
 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