GN: Add an option to build against the Debian wheezy sysroot

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 3bfa76eb0d3369790cad54e83e734282c1695957..b29e88bb22781936f2dcdd4e63e19b6e7b79c2e2 100644
--- a/DEPS
+++ b/DEPS
@@ -556,6 +556,20 @@ hooks = [
     ],
   },
   {
+    # Pull Debian wheezy sysroot for i386 Linux
+    'name': 'sysroot_i386',
+    'pattern': '.',
+    'action': ['python', 'sdk/build/linux/sysroot_scripts/install-sysroot.py',
+               '--running-as-hook', --arch', 'i386'],
+  },
+  {
+    # Pull Debian wheezy sysroot for amd64 Linux
+    'name': 'sysroot_amd64',
+    'pattern': '.',
+    'action': ['python', 'sdk/build/linux/sysroot_scripts/install-sysroot.py',
+               '--running-as-hook', '--arch', 'amd64'],
+  },
+  {
     # Pull clang if needed or requested via GYP_DEFINES.
     'name': 'gn_clang',
     'pattern': '.',