Livedisk-efi.iso build fails

make all works fine, livedisk-efi.iso fails

sahaj@ric-ubuntu:~/redox$ make build/livedisk-efi.iso
env --unset=XARGO_RUST_SRC make -C bootloader-efi build/redox_bootloader/boot.efi
make[1]: Entering directory '/home/sahaj/redox/bootloader-efi’
mkdir -p build/redox_bootloader
xargo rustc --lib --target x86_64-efi-pe --release – -C soft-float -C lto --emit link=build/redox_bootloader/boot.a
error: rust-src component not found. Run rustup component add rust-src.
note: run with RUST_BACKTRACE=1 for a backtrace
Makefile:74: recipe for target ‘build/redox_bootloader/boot.a’ failed
make[1]: *** [build/redox_bootloader/boot.a] Error 1
make[1]: Leaving directory '/home/sahaj/redox/bootloader-efi’
mk/disk.mk:28: recipe for target ‘bootloader-efi/build/redox_bootloader/boot.efi’ failed
make: *** [bootloader-efi/build/redox_bootloader/boot.efi] Error 2