Hello!
I'm having some trouble building rust 1.12 on Mac OS X 10.11.6 with Xcode 8.0. I'm bootstrapping with rust 1.11 but it looks like the stage0 compiler isn't working:
CFG_LLVM_LINKAGE_FILE=/opt/local/var/macports/build/_opt_local_var_macports_sources_svn.macports.org_dports_lang_rust/rust/work/rustc-1.12.0/x86_64-apple-darwin/rt/llvmdeps.rs DYLD_LIBRARY_PATH=/opt/local/var/macports/build/_opt_local_var_macports_sources_svn.macports.org_dports_lang_rust/rust/work/rustc-1.12.0/x86_64-apple-darwin/stage0/lib:/opt/local/var/macports/build/_opt_local_var_macports_sources_svn.macports.org_dports_lang_rust/rust/work/rustc-1.12.0/x86_64-apple-darwin/llvm/lib:$DYLD_LIBRARY_PATH x86_64-apple-darwin/stage0/bin/rustc --cfg stage0 -O --cfg rtopt -C rpath -C prefer-dynamic -C no-stack-check --target=x86_64-apple-darwin -L "x86_64-apple-darwin/rt" -L native="/opt/local/var/macports/build/_opt_local_var_macports_sources_svn.macports.org_dports_lang_rust/rust/work/rustc-1.12.0/x86_64-apple-darwin/llvm/lib" --out-dir x86_64-apple-darwin/stage0/lib/rustlib/x86_64-apple-darwin/lib -C extra-filename=-40393716 -C metadata=40393716 src/librustc_platform_intrinsics/lib.rs
error: linking with `cc` failed: exit code: 1
the full build log is here. From other reports it looks like it builds fine on macOS Sierra.