git clone git@github.com:rust-lang/rust.git
cd rust
git checkout 1.2.0
./configure --target=armv7-apple-ios,armv7s-apple-ios,i386-apple-ios,aarch64-apple-ios,x86_64-apple-ios --prefix=$HOME/rustc-ios
make -j8

rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/libstd
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `armv7-apple-ios`
warning: dropping unsupported crate type `dylib` for target `armv7s-apple-ios`
rustc: x86_64-apple-darwin/stage2/lib/rustlib/aarch64-apple-ios/lib/libstd
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `aarch64-apple-ios`
warning: dropping unsupported crate type `dylib` for target `x86_64-apple-ios`
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd
rustc: x86_64-apple-darwin/stage2/lib/rustlib/i386-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `i386-apple-ios`
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of unstable library feature 'result_fold': has not seen enough usage to justify its position in the standard library
src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                         ^~~~~~~~~~~~
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 help: add #![feature(result_fold)] to the crate attributes to enable
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of deprecated item: has not seen enough usage to justify its position in the standard library, #[deny(deprecated)] on by default
src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                         ^~~~~~~~~~~~
error: aborting due to 2 previous errors
make: *** [x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/stamp.std] Error 101
make: *** Waiting for unfinished jobs....
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of unstable library feature 'result_fold': has not seen enough usage to justify its position in the standard library
src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                         ^~~~~~~~~~~~
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 help: add #![feature(result_fold)] to the crate attributes to enable
src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of deprecated item: has not seen enough usage to justify its position in the standard library, #[deny(deprecated)] on by default
src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                         ^~~~~~~~~~~~
error: aborting due to 2 previous errors
make: *** [x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/stamp.std] Error 101