Search all bionic subdirectories

Some bionic subdirectories need to be built with soong, and others with
makefiles.  Search the bionic subdirectories invidivdually so the
bionic/Android.bp file doesn't prevent bionic/Android.mk from being parsed.

Change-Id: I66846f0175a5a01266adc0b792820bb82ffd1e14
diff --git a/root.bp b/root.bp
index a0b79f7..6f20832 100644
--- a/root.bp
+++ b/root.bp
@@ -3,7 +3,7 @@
 subdirs = [
     "build/blueprint",
     "build/soong",
-    "bionic",
+    "bionic/*",
     "dalvik",
     "external/*",
     "frameworks/base",