Add a snapshot of flutter/engine/src/build to our sdk

build/config/fnl/BUILD.gn

Index: build/config/fnl/BUILD.gn
diff --git a/build/config/fnl/BUILD.gn b/build/config/fnl/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..0eb35e3499b7b1edee4785234c2d7973a8853b63
--- /dev/null
+++ b/build/config/fnl/BUILD.gn
@@ -0,0 +1,48 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/linux/pkg_config.gni")
+import("//build/config/features.gni")
+import("//build/config/sysroot.gni")
+import("//build/config/ui.gni")
+
+config("sdk") {
+  if (sysroot != "") {
+    cflags = [ "--sysroot=" + sysroot ]
+    ldflags = [ "--sysroot=" + sysroot ]
+
+    # Need to get some linker flags out of the sysroot.
+    ldflags += [ exec_script("../linux/sysroot_ld_path.py",
+                             [
+                               rebase_path("//build/linux/sysroot_ld_path.sh",
+                                           root_build_dir),
+                               sysroot,
+                             ],
+                             "value") ]
+  }
+
+  defines = [ "FNL_MUSL" ]
+
+  if (use_ozone) {
+    defines += [ "MESA_EGL_NO_X11_HEADERS" ]
+  }
+}
+
+config("fontconfig") {
+  libs = [ "fontconfig" ]
+}
+
+pkg_config("freetype2") {
+  packages = [ "freetype2" ]
+}
+
+if (use_evdev_gestures) {
+  pkg_config("libevdev-cros") {
+    packages = [ "libevdev-cros" ]
+  }
+
+  pkg_config("libgestures") {
+    packages = [ "libgestures" ]
+  }
+}