Build 01

[andrewbird]

This PR aims to:

• Make the build process more OS agnostic.
• Add a second functional compiler choice (GCC ia16 cross compiler)
• Reduce memory consumption on GCC by means of creative linking
• Adds IBM Interrupt Sharing Protocol header to resident code for better interoperability with debuggers and other TSR that want to hook int2f

Type	Turbo C 2.01	Gcc ia16
File size (bytes)	6300	5336
Resident size (paragraphs)	0x0240	0x01bb

Tested GCC using Dosemu2 test 'test_fat_ds3_share_open_twice' and shows identical results to TCC 2.01