Add minimal required abseil BUILD.gn

This is the minimum required to support cobalt's current build

Change-Id: Ic52f13140567e285e33a549fc925092b482b0adf
diff --git a/BUILD.gn b/BUILD.gn
new file mode 100644
index 0000000..a074def
--- /dev/null
+++ b/BUILD.gn
@@ -0,0 +1,15 @@
+# Copyright 2018 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("abseil-cpp") {
+  public_deps = [
+    "//third_party/abseil-cpp/absl",
+  ]
+}
+
+config("abseil_config") {
+  include_dirs = [
+    "//third_party/abseil-cpp",
+  ]
+}
diff --git a/absl/BUILD.gn b/absl/BUILD.gn
new file mode 100644
index 0000000..e3dd308
--- /dev/null
+++ b/absl/BUILD.gn
@@ -0,0 +1,11 @@
+# Copyright 2018 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("absl") {
+  public_configs = ["//third_party/abseil-cpp:abseil_config"]
+
+  public_deps = [
+    "//third_party/abseil-cpp/absl/strings"
+  ]
+}
diff --git a/absl/base/BUILD.gn b/absl/base/BUILD.gn
new file mode 100644
index 0000000..4440f8e
--- /dev/null
+++ b/absl/base/BUILD.gn
@@ -0,0 +1,16 @@
+# Copyright 2018 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("core_headers") {
+  public_configs = ["//third_party/abseil-cpp:abseil_config"]
+
+  sources = [
+    "attributes.h",
+    "macros.h",
+    "optimization.h",
+    "port.h",
+    "thread_annotations.h",
+  ]
+}
+
diff --git a/absl/strings/BUILD.gn b/absl/strings/BUILD.gn
new file mode 100644
index 0000000..8f9b8dd
--- /dev/null
+++ b/absl/strings/BUILD.gn
@@ -0,0 +1,18 @@
+# Copyright 2018 The Fuchsia Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("strings") {
+  public_configs = ["//third_party/abseil-cpp:abseil_config"]
+
+  sources = [
+    "escaping.h",
+    "escaping.cc",
+    "str_cat.h",
+    "str_cat.cc",
+  ]
+
+  deps = [
+    "//third_party/abseil-cpp/absl/base:core_headers",
+  ]
+}