enable developers to provide their own android toolchain

platform_tools/android/bin/utils/setup_toolchain.sh

+#!/bin/bash
+#
+# setup_toolchain.sh: Sets toolchain environment variables used by other scripts.
+
+# Fail-fast if anything in the script fails.
+set -e
+
+# check that the preconditions for this script are met
+if [ $(type -t verbose) != 'function' ]; then
+  echo "ERROR: The verbose function is expected to be defined"
+  return 1
+fi
+
+if [ $(type -t exportVar) != 'function' ]; then
+  echo "ERROR: The exportVar function is expected to be defined"
+  return 1
+fi
+
+if [ $(type -t absPath) != 'function' ]; then
+  echo "ERROR: The absPath function is expected to be defined"
+  return 1
+fi
+
+if [ -z "$SCRIPT_DIR" ]; then
+  echo "ERROR: The SCRIPT_DIR variable is expected to be defined"
+  return 1
+fi
+
+function default_toolchain() {
+  API_LEVEL=14
+  NDK_REV=${NDK_REV-8e}
+  ANDROID_ARCH=${ANDROID_ARCH-arm}
+
+  TOOLCHAIN_DIR=${SCRIPT_DIR}/../toolchains
+  if [ $(uname) == "Darwin" ]; then
+    verbose "Using Mac toolchain."
+    TOOLCHAIN_TYPE=ndk-r$NDK_REV-$ANDROID_ARCH-mac_v$API_LEVEL
+  else
+    verbose "Using Linux toolchain."
+    TOOLCHAIN_TYPE=ndk-r$NDK_REV-$ANDROID_ARCH-linux_v$API_LEVEL
+  fi
+  exportVar ANDROID_TOOLCHAIN "${TOOLCHAIN_DIR}/${TOOLCHAIN_TYPE}/bin"
+
+  # if the toolchain doesn't exist on your machine then we need to fetch it
+  if [ ! -d "$ANDROID_TOOLCHAIN" ]; then
+    mkdir -p $TOOLCHAIN_DIR
+    # enter the toolchain directory then download, unpack, and remove the tarball
+    pushd $TOOLCHAIN_DIR
+    TARBALL=ndk-r$NDK_REV-v$API_LEVEL.tgz
+
+    ${SCRIPT_DIR}/download_toolchains.py \
+        http://chromium-skia-gm.commondatastorage.googleapis.com/android-toolchains/$TARBALL \
+        $TOOLCHAIN_DIR/$TARBALL
+    tar -xzf $TARBALL $TOOLCHAIN_TYPE
+    rm $TARBALL
+    popd
+  fi 
+
+  verbose "Targeting NDK API $API_LEVEL for use on Android 4.0 (NDK Revision $NDK_REV) and above"  
+}
+
+#check to see if the toolchain has been defined and if not setup the default toolchain
+if [ -z "$ANDROID_TOOLCHAIN" ]; then
+  default_toolchain
+  if [ ! -d "$ANDROID_TOOLCHAIN" ]; then
+    echo "ERROR: unable to download/setup the required toolchain (${ANDROID_TOOLCHAIN})"
+    return 1;
+  fi
+fi
+
+GCC=$(command ls $ANDROID_TOOLCHAIN/*-gcc | head -n1)
+if [ -z "$GCC" ]; then
+  echo "ERROR: Could not find Android cross-compiler in: $ANDROID_TOOLCHAIN"
+  return 1
+fi
+
+# Remove the '-gcc' at the end to get the full toolchain prefix
+ANDROID_TOOLCHAIN_PREFIX=${GCC%%-gcc}
+
+CCACHE=${ANDROID_MAKE_CCACHE-$(which ccache || true)}
+
+exportVar CC "$CCACHE $ANDROID_TOOLCHAIN_PREFIX-gcc"
+exportVar CXX "$CCACHE $ANDROID_TOOLCHAIN_PREFIX-g++"
+exportVar LINK "$CCACHE $ANDROID_TOOLCHAIN_PREFIX-gcc"
+
+exportVar AR "$ANDROID_TOOLCHAIN_PREFIX-ar"
+exportVar RANLIB "$ANDROID_TOOLCHAIN_PREFIX-ranlib"
+exportVar OBJCOPY "$ANDROID_TOOLCHAIN_PREFIX-objcopy"
+exportVar STRIP "$ANDROID_TOOLCHAIN_PREFIX-strip"
+
+# Create symlinks for nm & readelf and add them to the path so that the ninja
+# build uses them instead of attempting to use the one on the system.
+# This is required to build using ninja on a Mac.
+ln -sf $ANDROID_TOOLCHAIN_PREFIX-nm $ANDROID_TOOLCHAIN/nm
+ln -sf $ANDROID_TOOLCHAIN_PREFIX-readelf $ANDROID_TOOLCHAIN/readelf
+exportVar PATH $ANDROID_TOOLCHAIN:$PATH