Fix building with current rust
Print out the rustc version before each build
Fix a flaky test while the compiler is changing
auto merge of #450 : alexcrichton/cargo/fix-cargo, r=alexcrichton
Revert "Revert "Use libgit2 for driving git instead of the CLI""

This reverts commit 04440bb035082d4163f2211af447b8d67e077ccb.

Conflicts:
	src/cargo/sources/git/utils.rs
Update git2-rs with mingw support

An upstream PR for libgit2 was applied locally, modified to build, and then
git2-rs was updated to use this small for of libgit2. This adds https support
via winhttp on mingw for windows users.