ART: Support dlopen for a PIC boot image

Add support for the recent dlext extension for PIC support. Pass
the oat_file_begin to dlopen_ext as a reserved_addr using the new
LOAD_AT_FIXED_ADDRESS flag (when it isn't null).

Bug: 24683631
Change-Id: I59c5c82aebfa7cfb815e1fcf47fd72bec6f8239b
1 file changed