Svd2Ada doesn't properly resolve relative paths pass in as Output_Dir

[Joebeazelman]

Svd2Ada doesn't resolve the Output_Dir if it's a relative path, leading to an GNAT.DIRECTORY_OPERATIONS error. This happens on MacOS X, but not sure about any of other platforms as I haven't tested it.

svd2ada "LPC176x5x.svd" --boolean -o "../../src" -p svd --base-types-package HAL --gen-uint-always

a_0.1.0_6eb0b591/bin/svd2ada terminated by unhandled exception
raised GNAT.DIRECTORY_OPERATIONS.DIRECTORY_ERROR : g-dirope.adb:617
Load address: 0x10b398000
Call stack traceback locations:
0x10b56b5f4 0x10b405ad0 0x10b4803c8 0x10b39a09d 0x10b5ec03c