Add ios build script for building iOS library.

This build script (iosbuild.sh) will build for following platforms:
iPhoneSimulator, iPhoneOS-V7 & iPhoneOS-V7s

Change-Id: Icbb69e00277a4164f848b8766089302e299506e0

iosbuild.sh

@@ -0,0 +1,92 @@
+#!/bin/bash
+#
+# This script generates 'WebP.framework'. An iOS app can decode WebP images
+# by including 'WebP.framework'.
+#
+# Run ./iosbuild.sh to generate 'WebP.framework' under the current directory
+# (previous build will be erased if it exists).
+#
+# This script is inspired by the build script written by Carson McDonald.
+# (http://www.ioncannon.net/programming/1483/using-webp-to-reduce-native-ios-app-size/).
+
+set -e
+
+# Extract the latest SDK version from the final field of the form: iphoneosX.Y
+declare -r SDK=$(xcodebuild -showsdks \
+  | grep iphoneos | sort | tail -n 1 | awk '{ print substr($NF, 9)}'
+)
+declare -r OLDPATH=${PATH}
+
+# Add iPhoneOS-V6 to the list of platforms below if you need armv6 support.
+# Note that iPhoneOS-V6 support is not available with the iOS6 SDK.
+declare -r PLATFORMS="iPhoneSimulator iPhoneOS-V7 iPhoneOS-V7s"
+declare -r SRCDIR=$(dirname $0)
+declare -r TOPDIR=$(pwd)
+declare -r BUILDDIR="${TOPDIR}/iosbuild"
+declare -r TARGETDIR="${TOPDIR}/WebP.framework"
+declare -r DEVELOPER=$(xcode-select --print-path)
+declare -r PLATFORMSROOT="${DEVELOPER}/Platforms"
+declare -r LIPO=$(xcrun -sdk iphoneos${SDK} -find lipo)
+LIBLIST=''
+
+if [[ -z "${SDK}" ]]; then
+  echo "iOS SDK not available"
+  exit 1
+elif [[ ${SDK} < 4.0 ]]; then
+  echo "You need iOS SDK version 4.0 or above"
+  exit 1
+else
+  echo "iOS SDK Version ${SDK}"
+fi
+
+rm -rf ${BUILDDIR}
+rm -rf ${TARGETDIR}
+mkdir -p ${BUILDDIR}
+mkdir -p ${TARGETDIR}/Headers/
+
+[[ -e ${SRCDIR}/configure ]] || (cd ${SRCDIR} && sh autogen.sh)
+
+for PLATFORM in ${PLATFORMS}; do
+  if [[ "${PLATFORM}" == "iPhoneOS-V7s" ]]; then
+    PLATFORM="iPhoneOS"
+    ARCH="armv7s"
+  elif [[ "${PLATFORM}" == "iPhoneOS-V7" ]]; then
+    PLATFORM="iPhoneOS"
+    ARCH="armv7"
+  elif [[ "${PLATFORM}" == "iPhoneOS-V6" ]]; then
+    PLATFORM="iPhoneOS"
+    ARCH="armv6"
+  else
+    ARCH="i386"
+  fi
+
+  ROOTDIR="${BUILDDIR}/${PLATFORM}-${SDK}-${ARCH}"
+  mkdir -p "${ROOTDIR}"
+
+  export DEVROOT="${PLATFORMSROOT}/${PLATFORM}.platform/Developer"
+  export SDKROOT="${DEVROOT}/SDKs/${PLATFORM}${SDK}.sdk"
+
+  export CFLAGS="-arch ${ARCH} -pipe -isysroot ${SDKROOT}"
+  export CXXFLAGS=${CFLAGS}
+  export LDFLAGS="-arch ${ARCH} -pipe -isysroot ${SDKROOT}"
+  export PATH="${DEVROOT}/usr/bin:${OLDPATH}"
+
+  ${SRCDIR}/configure --host=${ARCH}-apple-darwin --prefix=${ROOTDIR} \
+    --disable-shared --enable-static \
+    --enable-libwebpdecoder --enable-swap-16bit-csp
+
+  # run make only in the src/ directory to create libwebpdecoder.a
+  cd src/
+  make
+  make install
+
+  LIBLIST+=" ${ROOTDIR}/lib/libwebpdecoder.a"
+
+  make clean
+  cd ..
+
+  export PATH=${OLDPATH}
+done
+
+cp -a src/webp/* ${TARGETDIR}/Headers/
+${LIPO} -create ${LIBLIST} -output ${TARGETDIR}/WebP