gn2bp: Add -UANDROID for host supported targets

* Base now builds under multi-architectures.

Test: m cronet_aml_base_base
Change-Id: Ia672c79c51763d43258510c5e63eb609e465bfba
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index fcb7bb3..cf8a4fd 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -132,7 +132,7 @@
         ('rtti', True), # go/undefined-symbol-typeinfo
     ],
     'cronet_aml_base_base': [
-        ('header_libs', set(["media_ndk_headers"])),
+        ('header_libs', {"media_ndk_headers"}),
     ],
 }
 
@@ -963,8 +963,8 @@
   # So adding -UANDROID to cancel default -DANDROID if it's not specified.
   # This is needed for some targets(e.g. symbolize)
   # TODO: Set -UANDROID considering common define
-  # if "ANDROID" not in defines:
-  #   cflags.add("-UANDROID")
+  if "ANDROID" not in defines:
+    cflags.add("-UANDROID")
   return cflags
 
 def set_module_flags(module, cflags, defines):