GN: add sanitize arg

tools/xsan_build

-#!/bin/bash
-
-# Build Skia with one of Clang's many sanitizers.
-#
-# $ tools/xsan_build {address,thread,undefined,etc.} [any other flags to pass to make...]
-#
-# This script assumes the use of Clang >=3.2.
-#
-# For more information, see:
-#   http://clang.llvm.org/docs/UsersManual.html#controlling-code-generation
-
-set -e
-set -x
-
-here=$(cd `dirname $0`; echo `pwd`)
-cores=48
-
-echo "Bootstrapping CMake"
-pushd $here/../third_party/externals/cmake
-./bootstrap --parallel=$cores
-make -j $cores cmake
-popd
-
-cmake=$here/../third_party/externals/cmake/bin/cmake
-
-echo "Building Clang"
-pushd $here/../third_party/externals/llvm
-mkdir -p out/
-cd out/
-rm -f CMakeCache.txt   # Force CMake to re-configure, in case DEPS has changed.
-$cmake -DCMAKE_BUILD_TYPE=Release -G Ninja ..
-ninja
-popd
-
-export CC=$here/../third_party/externals/llvm/out/bin/clang
-export CXX=$here/../third_party/externals/llvm/out/bin/clang++
-$CC --version
-
-if [[ "$1" == "memory" ]]; then
-    echo "Building libc++ with MSAN"
-    pushd $here/../third_party/externals/llvm
-    mkdir -p msan_out/
-    cd msan_out/
-    rm -f CMakeCache.txt   # Force CMake to re-configure, in case DEPS has changed.
-    $cmake -DLLVM_USE_SANITIZER=MemoryWithOrigins -DCMAKE_BUILD_TYPE=Release -G Ninja ..
-    ninja cxx cxxabi   # No need to build all of LLVM+Clang with MSAN, just libc++.
-    popd
-
-    msan_out=$here/../third_party/externals/llvm/msan_out
-
-    export GYP_DEFINES="skia_gpu=0 skia_no_fontconfig=1 skia_freetype_static=1 ${GYP_DEFINES}"
-    export CXXFLAGS="-stdlib=libc++ -I$msan_out/include ${CXX_FLAGS}"
-    export LDFLAGS="-stdlib=libc++ -L$msan_out/lib -Wl,-rpath,$msan_out/lib ${LDFLAGS}"
-fi
-export GYP_DEFINES="skia_sanitizer=$1 ${GYP_DEFINES}"
-
-shift
-make $@