add android ndk (#326)

packages/n/ndk/xmake.lua

@@ -0,0 +1,35 @@
+package("ndk")
+
+    set_kind("toolchain")
+    set_homepage("https://developer.android.com/ndk")
+    set_description("Android NDK toolchain.")
+
+    local versions = {["21"] = "r21e"}
+    if is_host("windows") then
+        set_urls("https://dl.google.com/android/repository/android-ndk-$(version)-windows-x86_64.zip", {version = function (version)
+            return versions[tostring(version)]
+        end})
+        add_versions("21", "f71307c5c572e2c163d602b3704b8bc024bec0c43ba2800de36bd10f3a21492b")
+    elseif is_host("linux") then
+        set_urls("https://dl.google.com/android/repository/android-ndk-$(version)-linux-x86_64.zip", {version = function (version)
+            return versions[tostring(version)]
+        end})
+        add_versions("21", "ad7ce5467e18d40050dc51b8e7affc3e635c85bd8c59be62de32352328ed467e")
+    elseif is_host("macosx") then
+        set_urls("https://dl.google.com/android/repository/android-ndk-$(version)-darwin-x86_64.zip", {version = function (version)
+            return versions[tostring(version)]
+        end})
+        add_versions("21", "437278103a3db12632c05b1be5c41bbb8522791a67e415cc54411a65366f499d")
+    end
+
+    on_install("@windows", "@msys", "@linux", "@macosx", function (package)
+        os.vcp("*", package:installdir())
+    end)
+
+    on_test(function (package)
+        local host = os.host()
+        if host == "macosx" then
+            host = "darwin"
+        end
+        os.vrunv(path.join(package:installdir(), "toolchains/llvm/prebuilt", host .. "-x86_64", "bin/clang"), {"--version"})
+    end)