MFC r275867:

MFC r275867:

  Fix sporadic build failures due to race when running make installworld
  when strip gets replaced at install time by adding it to ITOOLS for the
  default usr.bin/xinstall STRIP_CMD

  This will fix the failure noted in this Jenkins build step:
  https://jenkins.freebsd.org/job/Build-UFS-image/688/

  This will also fix the issue reported by alfred@ dealing with installing on
  targets that differ from build hosts (e.g. installing on i386/i386 when built
  on amd64/amd64)

  Sponsored by: EMC / Isilon Storage Division

git-svn-id: svn://svn.freebsd.org/base/stable/10@276311 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f