Correct elftoolchain strip(1) memory size calculation

Calculate the segment's memory size (p_memsz) using the virtual
addresses, not the file offsets. Otherwise padding preceeding SHT_NOBITS
sections may be excluded from the calculation, resulting in a segment
that is too small.

PR:		195653
Sponsored by:	The FreeBSD Foundation


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275810 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f