[Build] Make premake-androidmk generate something

third_party/cpptoml.lua

@@ -1,7 +1,12 @@
 group("third_party")
 project("cpptoml")
   uuid("1e86cc51-3f8b-476d-9249-3b200424846b")
-  kind("Utility")
+  if os.istarget("android") then
+    -- ndk-build only supports StaticLib and SharedLib.
+    kind("StaticLib")
+  else
+    kind("Utility")
+  end
   language("C++")
   files({
     "cpptoml/include/cpptoml.h",

third_party/cxxopts.lua

@@ -1,7 +1,12 @@
 group("third_party")
 project("cxxopts")
   uuid("8b68cbe8-2da4-4f28-be14-9352eafa3168")
-  kind("Utility")
+  if os.istarget("android") then
+    -- ndk-build only supports StaticLib and SharedLib.
+    kind("StaticLib")
+  else
+    kind("Utility")
+  end
   language("C++")
   files({
     "cxxopts/include/cxxopts.hpp",