Add hostegl bld.inf info for building exporting and building the library. Note: uses tools/x86tool extension from /sftools/dev/hostenv/cpptoolsplat/symport/flm, which doesn't quite work right yet. SYS_INCLUDES needs adding to .xml, for example. Fixup warnings in hostegl when built using GCC.

<?xml version="1.0"?>
<PackageMap root="sf" layer="adapt" />