message: Improve prepare_libcore.sh
diff: #!/bin/bash --verbose
  +set -e
  +
  SRC_DIR="target/libcore"
  -rm -rf $SRC_DIR &&
  -mkdir -p $SRC_DIR/src &&
  +rm -rf $SRC_DIR
  +mkdir -p $SRC_DIR/src
  cp -r $(dirname $(rustup which rustc))/../lib/rustlib/src/rust/src/libcore $SRC_DIR/src/libcore || (echo "Please install rust-src component"; exit 1)
  -cd $SRC_DIR || exit 1
  -git init || exit 1
  -git add . || exit 1
  -git commit -m "Initial commit" -q || exit 1
  -git apply ../../000*.patch || exit 1
  +cd $SRC_DIR
  +git init
  +git add .
  +git commit -m "Initial commit" -q
  +git apply ../../000*.patch
  +
  echo "Successfully prepared libcore for building"
  