use latest xargo; this fixes the libstd build problem

Author: RalfJung

.travis.yml

@@ -7,7 +7,7 @@ before_script:
 - rustup target add i686-pc-windows-gnu
 - rustup target add i686-pc-windows-msvc
 - rustup component add rust-src
-- cargo install xargo
+- cargo install --git https://github.com/japaric/xargo.git
 - export RUST_SYSROOT=$HOME/rust
 script:
 - set -e

xargo/build.sh

@@ -1,4 +1,3 @@
 #!/bin/sh
 cd "$(dirname "$0")"
-sed 's/gcc = "0\.3\.50"/gcc = "=0\.3\.50"/' -i ~/.rustup/toolchains/*/lib/rustlib/src/rust/src/libstd/Cargo.toml
 RUSTFLAGS='-Zalways-encode-mir -Zmir-emit-validate=1' xargo build