MFC r292584:

MFC r292584:

  Set env vars from values on the efi loader command line.

  Examine each cmdline arg and if it contains an '=' convert it to ascii and
  pass it to putenv(). This allows var=value settings to come in on the
  command line.

  This will allow overriding dhcp server-provided data in loader(8), as
  discussed in PR 202098

PR:           202098
Relnotes:	Yes (this goes together with r294343)

git-svn-id: svn://svn.freebsd.org/base/stable/10@294345 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f