Misc fixes

[andre-richter]

Hi phil,

small PR here:

• Fixes pwd command substitution in README
• Fixes target file name in README
• Makes the target json a bit more intuitive to read by using long option argument for the linker. The short one can be confusing if you have no experience with ld.

By the way, I tried if switching to lld is straight-forward, but it throws an error if you just exchange the linker flavor:

error: linking with `lld` failed: exit code: 1
  |
  = note: "lld" "-flavor" "gnu" "--script=linker.ld" "-L" "/home/arichter/.xargo/lib/rustlib/x86_64-bootloader/lib" "/home/arichter/repos/bootloader/target/x86_64-bootloader/release/deps/bootloader-484e5291b10a3861.bootloader0.rcgu.o" "-o" "/home/arichter/repos/bootloader/target/x86_64-bootloader/release/deps/bootloader-484e5291b10a3861" "--gc-sections" "-L" "/home/arichter/repos/bootloader/target/x86_64-bootloader/release/deps" "-L" "/home/arichter/repos/bootloader/target/release/deps" "-L" "/home/arichter/.xargo/lib/rustlib/x86_64-bootloader/lib" "-Bstatic" "/home/arichter/repos/bootloader/target/x86_64-bootloader/release/deps/librlibc-d40895cb3b906a9b.rlib" "-Bdynamic"
  = note: lld: error: bootloader0-5c45d0f13b04536f6388a70c7a9344c0.rs:(.second_stage+0xA5): unrecognized reloc 13
          lld: error: bootloader0-5c45d0f13b04536f6388a70c7a9344c0.rs:(.second_stage+0x1A2): unrecognized reloc 13
          lld: error: bootloader0-5c45d0f13b04536f6388a70c7a9344c0.rs:(.second_stage+0x1CC): unrecognized reloc 13
          lld: error: bootloader0-5c45d0f13b04536f6388a70c7a9344c0.rs:(.second_stage+0x1F9): unrecognized reloc 13

[andre-richter]

Forgot to add objcopy changes as well. Its now synced with the travis commands. However, #6 still surfaces.

[phil-opp]

Thanks a lot!

By the way, I tried if switching to lld is straight-forward, but it throws an error if you just exchange the linker flavor

Yeah, I experienced that error as well. Seems like lld does not support some required 16-bit relocation yet.

However, #6 still surfaces.

The running instructions were created for an older version of the bootloader. Running it without a kernel is no longer possible. Maybe we could add a hello world kernel to the repo.