gn2bp: support building against Android's modp_b64

For experimental purposes only...

Test: builds
Change-Id: I08043bfc01dfa01e5a9bd02c4d20a7ee27d798ab
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index d8ddbde..cf8f1dd 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -152,6 +152,16 @@
   else:
     module.arch[arch].static_libs.add('libbrotli')
 
+def enable_modp_b64(module, arch):
+  # Requires crrev/c/4112845
+  # Requires aosp/2359455
+  # Requires aosp/2359456
+  if not module.is_compiled():
+    return
+  if arch is None:
+    module.static_libs.add('libmodpb64')
+  else:
+    module.arch[arch].static_libs.add('libmodpb64')
 
 def enable_zlib(module, arch):
   # Requires crrev/c/4109079
@@ -174,6 +184,8 @@
         enable_brotli,
     '//third_party/brotli:dec':
         enable_brotli,
+    '//third_party/modp_b64:modp_b64':
+        enable_modp_b64,
     '//third_party/zlib:zlib':
         enable_zlib,
 }