Replace egrep with obey file.
Old egrep loads grep using OS_File then after copying it will run it without calling Service_UKCompression.
As a result it fails to run on the Linux port of RISC OS as Unixlib's use of SVC mode is not patched.
Tested in BCM2835, IOMD32, OMAP3, OMAP4, OMAP5, Titanium, Tungsten, and iMx6 builds.
Also tested checkout with SimpleGit on RISC OS.
This the only change required to run ROM and Disc builds on the Linux Port.