Remove support for Ubuntu/Precise sysroot

build/experimental/install-build-deps.py

Index: build/experimental/install-build-deps.py
diff --git a/build/experimental/install-build-deps.py b/build/experimental/install-build-deps.py
index 1687b94b10336941d0a8db0cb8774f11aecd2806..04a26ab9d8f7692fb5e5c16d8a4831946294545c 100755
--- a/build/experimental/install-build-deps.py
+++ b/build/experimental/install-build-deps.py
@@ -13,7 +13,6 @@ import sys
 
 
 SUPPORTED_UBUNTU_VERSIONS = (
-  {'number': '12.04', 'codename': 'precise'},
   {'number': '14.04', 'codename': 'trusty'},
   {'number': '14.10', 'codename': 'utopic'},
   {'number': '15.04', 'codename': 'vivid'},
@@ -300,9 +299,7 @@ def compute_dynamic_package_lists():
   lsb_codename = lsb_release_short_codename()
 
   # Find the proper version of libstdc++6-4.x-dbg.
-  if lsb_codename == 'precise':
-    _packages_dbg += ('libstdc++6-4.6-dbg',)
-  elif lsb_codename == 'trusty':
+  if lsb_codename == 'trusty':
     _packages_dbg += ('libstdc++6-4.8-dbg',)
   else:
     _packages_dbg += ('libstdc++6-4.9-dbg',)