Hi,

Please find last update for patch that update rust and cargo in attachements.

Changes from last time:
1. Replaced jemalloc to 4.5.0 release according to
https://lists.gnu.org/archive/html/bug-guix/2017-12/msg00048.html
2. Added code that reset timestamps for rust build. When we change files
(through "substitute*" or with any other methods) their mtime changes,
but mtimes influent packages fingerprint and, as result,
"rust.metadata.bin" in "liblibc-<hash>.rlib" become not reproducible. 

Currently rustc build is reproducable.

Full list of changes from rustc 1.16:

1. Added GDB as test dependency
2. Added LLVM_LINK_SHARED environment variable to link with shared llvm
libraries (because there is no static libraries in guix llvm-3.9.1
package
3. rustc in 1.22.1 release try to find "ar" binary in same directory as
"gcc", but there is only "gcc-ar" in such place. *NOTE*: In next rust
release function "cc2ar" will be removed from and this "substitute*" will
be replaced with new option in config.toml
4. Ignored new test "connect_timeout_unroutable". This test failed in
container because there is no network.
5. Fixed bug in "up_to_date" function in "src/build_helper/lib.rs". This
fix already merged to rust repo in "master" branch.
6. Allow to fix shebangs in vendored sources. For this purpose was added
"patch-cargo-checksums" task that recreate ".cargo-checksum.json" for
all vendored sources and patch "src/Cargo.lock" to use patched vendored
sources.
7. Configuration performed through "config.toml" file instead of
obsolete "./configre" script.
8. Codegen tests was disabled, because 2 tests codegen/mainsubprogram.rs
and codegen/mainsubprogramstart.rs created for llvm with patch
backported from llvm 4.
9. After all this changes timestamps for sources resetted to achieve
reproducable build.
10. Build, test and installation preformed through new "./x.py" script
instead of obsolet makefiles generated by "./configure".

Full list of changes from cargo 1.17:
1. Tests was enabled!
2. New dependency for tests "git" utility.
3. Rust dependencies was updated from actual cargo's "Cargo.lock" file.
4. Return all "patch-*-shebngs" tasks. Without this patches some of
cargo dependencies fail to compile.
5. Recalculate ".cargo-checksum.json" files for all patched vendored
sources and update "Cargo.lock" to use this patched vendored sources.
6. Patch usage of "/usr/bin/env" in tests.
7. Disable next tests:
   * "wasm32_final_outputs" failed to call llvm for
   "asmjs-unknown-emscripten" architecture.
   * "ctrl_c_kills_everyone" fail in container because of network.
   * Added "CFG_DISABLE_CROSS_TESTS" to disable cross-compilation
   tests. Not fully understand issue with this tests, but according to
   cargo sources "This failure can be safely ignored".