Do not crash in cmake_transform.py is a module has no 'libs'

Bug: 154151802
Test: build
Signed-off-by: Roman Kiryanov <rkir@google.com>
Change-Id: Iaa3b4bf253daac9e6b9755cb31bb63d51273ef38
diff --git a/cmake_transform.py b/cmake_transform.py
index 3583ec8..298e454 100644
--- a/cmake_transform.py
+++ b/cmake_transform.py
@@ -106,7 +106,7 @@
     flags = [escape(d) for d in module['cflags'] if not d.startswith('-D')]
 
     # Make sure we remove the lib prefix from all our dependencies.
-    libs = [remove_lib_prefix(l) for l in module['libs']]
+    libs = [remove_lib_prefix(l) for l in module.get('libs', [])]
     staticlibs = [remove_lib_prefix(l) for l in
                       module.get('staticlibs', [])
                       if l != "libandroidemu"]