msan: build expat from source

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 80c6b183963b93a327d3f212b7d5cc3119c47d76..de69d8c51dfe659d293e2f8eb83387639faf7121 100644
--- a/DEPS
+++ b/DEPS
@@ -29,7 +29,7 @@ deps = {
   "third_party/externals/yasm/source/patched-yasm/" : "https://chromium.googlesource.com/chromium/deps/yasm/patched-yasm.git@4671120cd8558ce62ee8672ebf3eb6f5216f909b",
   "third_party/externals/yasm/binaries"             : "https://chromium.googlesource.com/chromium/deps/yasm/binaries.git@52f9b3f4b0aa06da24ef8b123058bb61ee468881",
 
-  "platform_tools/android/third_party/externals/expat" : "https://android.googlesource.com/platform/external/expat.git@android-5.1.0_r3",
+  "third_party/externals/expat" : "https://android.googlesource.com/platform/external/expat.git@android-5.1.0_r3",
 
   "platform_tools/chromeos/toolchain/src/third_party/chromite": "https://chromium.googlesource.com/chromiumos/chromite.git@d6a4c7e0ee4d53ddc5238dbddfc0417796a70e54",
   "platform_tools/chromeos/toolchain/src/third_party/pyelftools": "https://chromium.googlesource.com/chromiumos/third_party/pyelftools.git@bdc1d380acd88d4bfaf47265008091483b0d614e",