Bug 1135201: Use most-recent available gdb

Older versions of gdb don't support certain features, such as new
versions of the DWARF format in this case. Changing the prefered
gdb version to the most recent one ensures that we support as many
features as possible.

run-gdb.sh

@@ -28,9 +28,7 @@ esac
 HOST_OS=$(uname -s | tr "[[:upper:]]" "[[:lower:]]")-x86
 
 if [ -z "${GDB}" ]; then
-   if [ -d prebuilt ]; then
-      GDB=prebuilt/${HOST_OS}/toolchain/${TARGET_TRIPLE}-4.4.x/bin/${TARGET_TRIPLE}-gdb
-   elif [ -d prebuilts ]; then
+   if [ -d prebuilts ]; then
       GDB=prebuilts/gcc/${HOST_OS}/${TARGET_ARCH}/${TARGET_TRIPLE}-4.8/bin/${TARGET_TRIPLE}-gdb
       # If new version doesn't exist fallback to old version.
       [ -f "${GDB}" ] || GDB=prebuilts/gcc/${HOST_OS}/${TARGET_ARCH}/${TARGET_TRIPLE}-4.7/bin/${TARGET_TRIPLE}-gdb
@@ -39,6 +37,8 @@ if [ -z "${GDB}" ]; then
       if [ -d $PYTHON_DIR ]; then
         export PYTHONHOME=$PYTHON_DIR
       fi
+   elif [ -d prebuilt ]; then
+      GDB=prebuilt/${HOST_OS}/toolchain/${TARGET_TRIPLE}-4.4.x/bin/${TARGET_TRIPLE}-gdb
    else
       echo "Not sure where gdb is located. Override using GDB= or fix the script."
       exit 1