cros_sdk: move SDK_VERSION_FILE to buildbot.constants

This file needs to be read by cbuildbot too, so move the constant to a
common location.

While we're here, replace the local SRC_ROOT with constants.SOURCE_ROOT
since they represent the same thing.

BUG=chromium-os:36453
TEST=`./buildbot/run_tests` passes
TEST=`cros_sdk` works
TEST=`cros_sdk --chroot=new-chroot` works (downloads & installs sdk)

Change-Id: I04bf149de4518451a46860db006325c1204ab18d
Reviewed-on: https://gerrit.chromium.org/gerrit/40618
Reviewed-by: David James <davidjames@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_sdk.py b/scripts/cros_sdk.py
index a21caeb..9cc0748 100644
--- a/scripts/cros_sdk.py
+++ b/scripts/cros_sdk.py
@@ -23,14 +23,11 @@
 DEFAULT_URL = 'https://commondatastorage.googleapis.com/chromiumos-sdk'
 COMPRESSION_PREFERENCE = ('xz', 'bz2')
 
-SRC_ROOT = os.path.realpath(constants.SOURCE_ROOT)
-OVERLAY_DIR = os.path.join(SRC_ROOT, 'src/third_party/chromiumos-overlay')
-SDK_VERSION_FILE = os.path.join(OVERLAY_DIR,
-                                'chromeos/binhost/host/sdk_version.conf')
-
 # TODO(zbehan): Remove the dependency on these, reimplement them in python
-MAKE_CHROOT = [os.path.join(SRC_ROOT, 'src/scripts/sdk_lib/make_chroot.sh')]
-ENTER_CHROOT = [os.path.join(SRC_ROOT, 'src/scripts/sdk_lib/enter_chroot.sh')]
+MAKE_CHROOT = [os.path.join(constants.SOURCE_ROOT,
+                            'src/scripts/sdk_lib/make_chroot.sh')]
+ENTER_CHROOT = [os.path.join(constants.SOURCE_ROOT,
+                             'src/scripts/sdk_lib/enter_chroot.sh')]
 
 # We need these tools to run. Very common tools (tar,..) are ommited.
 NEEDED_TOOLS = ('curl', 'xz', 'unshare')
@@ -213,7 +210,9 @@
 to an interactive bash shell within the chroot.
 
 If given args those are passed to the chroot environment, and executed."""
-  conf = cros_build_lib.LoadKeyValueFile(SDK_VERSION_FILE, ignore_missing=True)
+  conf = cros_build_lib.LoadKeyValueFile(
+      os.path.join(constants.SOURCE_ROOT, constants.SDK_VERSION_FILE),
+      ignore_missing=True)
   sdk_latest_version = conf.get('SDK_LATEST_VERSION', '<unknown>')
   bootstrap_latest_version = conf.get('BOOTSTRAP_LATEST_VERSION', '<unknown>')
 
@@ -247,7 +246,8 @@
       help='Download the sdk.')
 
   # Global options:
-  default_chroot = os.path.join(SRC_ROOT, constants.DEFAULT_CHROOT_DIR)
+  default_chroot = os.path.join(constants.SOURCE_ROOT,
+                                constants.DEFAULT_CHROOT_DIR)
   parser.add_option(
       '--chroot', dest='chroot', default=default_chroot, type='path',
       help=('SDK chroot dir name [%s]' % constants.DEFAULT_CHROOT_DIR))
@@ -346,7 +346,7 @@
       osutils.SafeMakedirs(options.cache_dir)
 
       for target in (sdk_cache, distfiles_cache):
-        src = os.path.join(SRC_ROOT, os.path.basename(target))
+        src = os.path.join(constants.SOURCE_ROOT, os.path.basename(target))
         if not os.path.exists(src):
           osutils.SafeMakedirs(target)
           continue