bug: fix osx compilation issues

[prestwich]

I have verified that this succesfully exchanges packets with the device on osx

[tynes]

Verified the tests pass and then the tests fail if the ethereum app isn't opened on the ledger.

$ cargo test -- --nocapture
running 1 test
test common::test::serialize ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out


running 2 tests
APDUAnswer: {
	Response: Code 9000 ([APDU_CODE_NOERROR]) 
	Data: Some([2, 1, 2, 11])
}
test exchange ... ok
"IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/XHC1@14/XHC1@14000000/HS01@14100000/Nano S@14100000/Nano S@0/AppleUserUSBHostHIDDevice"
test ledger_device_path ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out


running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[tynes]

The app version printed matches the app version installed