Add script to create an Android RootFS (dotnet#15883)

.gitignore

@@ -28,6 +28,7 @@ msbuild.wrn
 
 # Cross building rootfs
 cross/rootfs/
+cross/android-rootfs/
 # add x86 as it is ignored in 'Build results'
 !cross/x86
 

cross/build-android-rootfs.sh

@@ -0,0 +1,108 @@
+#!/usr/bin/env bash
+
+usage()
+{
+    echo "Creates a toolchain and sysroot used for cross-compiling for Android."
+    echo.
+    echo "Usage: $0 [BuildArch] [ApiLevel]"
+    echo.
+    echo "BuildArch is the target architecture of Android. Currently only arm64 is supported."
+    echo "ApiLevel is the target Android API level. API levels usually match to Android releases. See https://source.android.com/source/build-numbers.html"
+    echo.
+    echo "By default, the toolchain and sysroot will be generated in cross/android-rootfs/toolchain/[BuildArch]. You can change this behavior"
+    echo "by setting the TOOLCHAIN_DIR environment variable"
+    echo.
+    echo "By default, the NDK will be downloaded into the cross/android-rootfs/android-ndk-r13b directory. If you already have an NDK installation,"
+    echo "you can set the NDK_DIR environment variable to have this script use that installation of the NDK."
+    exit 1
+}
+
+__ApiLevel=21 # The minimum platform for arm64 is API level 21
+__BuildArch=arm64
+__AndroidArch=aarch64
+
+for i in "$@"
+    do
+        lowerI="$(echo $i | awk '{print tolower($0)}')"
+        case $lowerI in
+        -?|-h|--help)
+            usage
+            exit 1
+            ;;
+        arm64)
+            __BuildArch=arm64
+            __AndroidArch=aarch64
+            ;;
+        *[0-9])
+            __ApiLevel=$i
+            ;;
+        *)
+            __UnprocessedBuildArgs="$__UnprocessedBuildArgs $i"
+            ;;
+    esac
+done
+
+# Obtain the location of the bash script to figure out where the root of the repo is.
+__CrossDir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+
+__Android_Cross_Dir="$__CrossDir/android-rootfs"
+__NDK_Dir="$__Android_Cross_Dir/android-ndk-r13b"
+__libunwind_Dir="$__Android_Cross_Dir/libunwind"
+__ToolchainDir="$__Android_Cross_Dir/toolchain/$__BuildArch"
+
+if [[ -n "$TOOLCHAIN_DIR" ]]; then
+    __ToolchainDir=$TOOLCHAIN_DIR
+fi
+
+if [[ -n "$NDK_DIR" ]]; then
+    __NDK_Dir=$NDK_DIR
+fi
+
+echo "Target API level: $__ApiLevel"
+echo "Target architecture: $__BuildArch"
+echo "NDK location: $__NDK_Dir"
+echo "Target Toolchain location: $__ToolchainDir"
+
+# Download the NDK if required
+if [ ! -d $__NDK_Dir ]; then
+    echo Downloading the NDK into $__NDK_Dir
+    mkdir -p $__NDK_Dir
+    wget -nv -nc --show-progress https://dl.google.com/android/repository/android-ndk-r13b-linux-x86_64.zip -O $__Android_Cross_Dir/android-ndk-r13b-linux-x86_64.zip
+    unzip -q $__Android_Cross_Dir/android-ndk-r13b-linux-x86_64.zip -d $__Android_Cross_Dir
+fi
+
+# Create the RootFS for both arm64 as well as aarch
+rm -rf $__Android_Cross_Dir/toolchain
+
+echo Generating the $__BuildArch toolchain
+$__NDK_Dir/build/tools/make_standalone_toolchain.py --arch $__BuildArch --api $__ApiLevel --install-dir $__ToolchainDir
+
+# Install the required packages into the toolchain
+rm -rf $__Android_Cross_Dir/deb/
+rm -rf $__Android_Cross_Dir/tmp
+
+mkdir -p $__Android_Cross_Dir/deb/
+mkdir -p $__Android_Cross_Dir/tmp/$arch/
+wget -nv -nc http://termux.net/dists/stable/main/binary-$__AndroidArch/libcurl-dev_7.52.1_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/libcurl-dev_7.52.1_$__AndroidArch.deb
+wget -nv -nc http://termux.net/dists/stable/main/binary-$__AndroidArch/libcurl_7.52.1_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/libcurl_7.52.1_$__AndroidArch.deb
+wget -nv -nc https://github.com/qmfrederik/dotnet-alpine-arm/raw/master/krb5-dev_1.15_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/krb5-dev_1.15_$__AndroidArch.deb
+wget -nv -nc https://github.com/qmfrederik/dotnet-alpine-arm/raw/master/krb5_1.15_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/krb5_1.15_$__AndroidArch.deb
+wget -nv -nc http://termux.net/dists/stable/main/binary-$__AndroidArch/openssl-dev_1.0.2k_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/openssl-dev_1.0.2k_$__AndroidArch.deb
+wget -nv -nc http://termux.net/dists/stable/main/binary-$__AndroidArch/openssl_1.0.2k_$__AndroidArch.deb -O $__Android_Cross_Dir/deb/openssl_1.0.2k_$__AndroidArch.deb
+
+echo Unpacking Termux packages
+dpkg -x $__Android_Cross_Dir/deb/libcurl-dev_7.52.1_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+dpkg -x $__Android_Cross_Dir/deb/libcurl_7.52.1_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+dpkg -x $__Android_Cross_Dir/deb/krb5-dev_1.15_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+dpkg -x $__Android_Cross_Dir/deb/krb5_1.15_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+dpkg -x $__Android_Cross_Dir/deb/openssl-dev_1.0.2k_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+dpkg -x $__Android_Cross_Dir/deb/openssl_1.0.2k_$__AndroidArch.deb $__Android_Cross_Dir/tmp/$__AndroidArch/
+
+cp -R $__Android_Cross_Dir/tmp/$__AndroidArch/data/data/com.termux/files/usr/* $__ToolchainDir/sysroot/usr/
+
+# ifaddrs.h is not available natively Android, but a version of it is available
+# See https://github.com/termux/termux-packages/issues/338 for context
+wget -nv -nc https://raw.githubusercontent.com/qnnnnez/android-ifaddrs/master/include/ifaddrs_single.h -O $__ToolchainDir/sysroot/usr/include/ifaddrs.h
+
+echo Now run:
+echo CONFIG_DIR=\`realpath cross/android/arm64\` ROOTFS_DIR=\`realpath $__ToolchainDir/sysroot\` ./build-native.sh -debug -buildArch=arm64 -- verbose cross