[mips backport] Don't build unnecessary SDL sources on OSX

These files don't compile with Xcode 4.4+ due to relying on
long-deprecated and now removed Carbon headers. Turns out the code in
them isn't actually used on OSX, and the upstream build system doesn't
try to build them.

(cherry picked from commit ad2342375963c2468849c1f83a97158383db6511)

Change-Id: Ieba3bf24b640e349156a4588cb36f9787db7d16d
[mips backport] Add host_toolchain_header path if defined

host_toolchain_header may be defined for build in MacOSX
when SDK 10.8 is selected in build/core/combo/HOST_darwin-x86.mk.
It points to prebuilts/gcc/darwin-x86/host/i686-apple-darwin-4.2.1/
lib/gcc/i686-apple-darwin1?/4.2.1/include for headers such as stdarg.h
no longer provided by MacOSX SDK since 10.8

See https://android-review.googlesource.com/#/c/46202

(cherry picked from commit a5d8f65199d1326457d233121fc9fe12d3eab460)

Change-Id: Ie41a1fa346e2ae72f06fc84a03c421da72393fac
Handle emulated NAND devices that are larger than 2GB

Change-Id: I002ae932b074fd10128ee346be9a611857cb36b9
Signed-off-by: Chris Dearman <chris@imgtec.com>