Make landmines.py take an extra script via an env var.

build/landmines.py

Index: build/landmines.py
diff --git a/build/landmines.py b/build/landmines.py
index f1a514c5e7e206c345a33febea6b3d840781999e..0df5455c7dc558f58f162fe5b94debc67d0a8bee 100755
--- a/build/landmines.py
+++ b/build/landmines.py
@@ -113,6 +113,14 @@ def main():
                               stdout=subprocess.PIPE)
       output, _ = proc.communicate()
       landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
+
+    extra_script = os.environ.get('EXTRA_LANDMINES_SCRIPT')
+    if extra_script:
+      proc = subprocess.Popen([sys.executable, extra_script, '-t', target],
+                              stdout=subprocess.PIPE)
+      output, _ = p.communicate()
+      landmines.extend([('%s\n' % l.strip()) for l in output.splitlines()])
+
     set_up_landmines(target, landmines)
 
   return 0