gn2bp: use chromium libc++ headers

Test: //base:base
Change-Id: I1d73f843fb55d83964cbf01fddc0df9a4192a665
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 52a8ed4..7ded1e8 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -830,6 +830,8 @@
     for flag in target.cflags:
       if '-std=' in flag:
         module.cpp_std = flag[len('-std='):]
+      if '-isystem' in flag:
+        module.local_include_dirs.add(flag[len('-isystem../../'):])
 
     # Adding local_include_dirs is necessary due to source_sets / filegroups
     # which do not properly propagate include directories.
@@ -929,6 +931,7 @@
       '-fvisibility=hidden',
       '-O2',
   ]
+  defaults.stl = 'none'
   blueprint.add_module(defaults)
 
   for target in targets: