prebuilt android tools: Init using SDK

Expose as an option for the cross stdenv.

pkgs/development/mobile/androidenv/androidndk-pkgs.nix

@@ -0,0 +1,82 @@
+{ lib, hostPlatform, targetPlatform
+, makeWrapper
+, runCommand, wrapBintoolsWith, wrapCCWith
+, buildAndroidndk, androidndk, targetAndroidndkPkgs
+}:
+
+let
+  # Mapping from a platform to information needed to unpack NDK stuff for that
+  # platform.
+  #
+  # N.B. The Android NDK uses slightly different LLVM-style platform triples
+  # than we do. We don't just use theirs because ours are less ambiguous and
+  # some builds need that clarity.
+  ndkInfoFun = { config, ... }: {
+    "x86_64-unknown-linux-gnu" = {
+      double = "linux-x86_64";
+    };
+    "arm-unknown-linux-androideabi" = {
+      arch = "arm";
+      triple = "arm-linux-androideabi";
+      gccVer = "4.8";
+    };
+    "aarch64-unknown-linux-android" = {
+      arch = "arm64";
+      triple = "aarch64-linux-android";
+      gccVer = "4.9";
+    };
+  }.${config} or
+    (throw "Android NDK doesn't support ${config}, as far as we know");
+
+  hostInfo = ndkInfoFun hostPlatform;
+  targetInfo = ndkInfoFun targetPlatform;
+
+in
+
+rec {
+  # Misc tools
+  binaries = let
+      ndkBinDir =
+        "${androidndk}/libexec/${androidndk.name}/toolchains/${targetInfo.triple}-${targetInfo.gccVer}/prebuilt/${hostInfo.double}/bin";
+    in runCommand "ndk-gcc-binutils" {
+      isGNU = true; # for cc-wrapper
+      nativeBuildInputs = [ makeWrapper ];
+      propgatedBuildInputs = [ androidndk ];
+    } ''
+      mkdir -p $out/bin
+      for prog in ${ndkBinDir}/${targetInfo.triple}-*; do
+        prog_suffix=$(basename $prog | sed 's/${targetInfo.triple}-//')
+        ln -s $prog $out/bin/${targetPlatform.config}-$prog_suffix
+      done
+    '';
+
+  binutils = wrapBintoolsWith {
+    bintools = binaries;
+    libc = targetAndroidndkPkgs.libraries;
+  };
+
+  gcc = wrapCCWith {
+    cc = binaries;
+    bintools = binutils;
+    libc = targetAndroidndkPkgs.libraries;
+    extraBuildCommands =
+      # GCC 4.9 is the first relase with "-fstack-protector"
+      lib.optionalString (lib.versionOlder targetInfo.gccVer "4.9") ''
+        sed -E \
+        -i $out/nix-support/add-hardening.sh \
+        -e 's|(-fstack-protector)-strong|\1|g'
+      '';
+  };
+
+  # Bionic lib C and other libraries.
+  #
+  # We use androidndk from the previous stage, else we waste time or get cycles
+  # cross-compiling packages to wrap incorrectly wrap binaries we don't include
+  # anyways.
+  libraries = {
+    name = "bionic-prebuilt";
+    type = "derivation";
+    outPath = "${buildAndroidndk}/libexec/${buildAndroidndk.name}/platforms/android-21/arch-${hostInfo.arch}/usr/";
+    drvPath = throw "fake derivation, build ${buildAndroidndk} to use";
+  };
+}

pkgs/development/mobile/androidenv/default.nix

@@ -242,4 +242,19 @@ rec {
     inherit (pkgs) stdenv;
     inherit androidsdk;
   };
+
+  androidndkPkgs = import ./androidndk-pkgs.nix {
+    inherit (buildPackages)
+      makeWrapper;
+    inherit (pkgs)
+      lib hostPlatform targetPlatform
+      runCommand wrapBintoolsWith wrapCCWith;
+    # buildPackages.foo rather than buildPackages.buildPackages.foo would work,
+    # but for splicing messing up on infinite recursion for the variants we
+    # *dont't* use. Using this workaround, but also making a test to ensure
+    # these two really are the same.
+    buildAndroidndk = buildPackages.buildPackages.androidenv.androidndk;
+    inherit androidndk;
+    targetAndroidndkPkgs = targetPackages.androidenv.androidndkPkgs;
+  };
 }