Port most of the remainder of //tools/android from GYP to GN

tools/android/purge_ashmem/BUILD.gn

Index: tools/android/purge_ashmem/BUILD.gn
diff --git a/device/bluetooth/uribeacon/BUILD.gn b/tools/android/purge_ashmem/BUILD.gn
similarity index 70%
copy from device/bluetooth/uribeacon/BUILD.gn
copy to tools/android/purge_ashmem/BUILD.gn
index 484e27270327646f886047b1d4d39d1a2e6641f1..e717fb137f6622d9b16db13a4f5b97eb81a7b49a 100644
--- a/device/bluetooth/uribeacon/BUILD.gn
+++ b/tools/android/purge_ashmem/BUILD.gn
@@ -2,12 +2,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("uribeacon") {
+executable("purge_ashmem") {
   sources = [
-    "uri_encoder.cc",
-    "uri_encoder.h",
+    "purge_ashmem.c",
   ]
   deps = [
-    "//base",
+    "//third_party/ashmem",
   ]
 }