Provide an option for the base/rom extension that causes the toolchain id (ARMCC or GCCE) to be defined for
the C preprocessor phase of rombuild, enabling rom files to be conditionally included or excluded depending
on whether the toolchain can build them. This mimics the same change for Beagleboard.
5c4b0c1fa5f84f299d50ad82f561454aa109a2a4 PDK_3.0.b
c506b18dc03fca6edca100e3b2cd2ae4c175215c PDK_3.0.c
c506b18dc03fca6edca100e3b2cd2ae4c175215c PDK_2.0.1
1a93ed2e38bd484d72fdaa19792e0f9568455b8a PDK_3.0.d
1a93ed2e38bd484d72fdaa19792e0f9568455b8a PDK_2.0.2
7048876724acc5d17377ab5ff1747863859d4efc PDK_3.0.e