futility: Link with libcrosid
futility: Link with libcrosid

Use pkg-config to link with libcrosid when it's available.

Note that when futility is compiled from the coreboot tree, libcrosid
won't be available, at least at the moment, so expose -DUSE_CROSID to
the C code so we know when we have it available.

BUG=b:213251232
BRANCH=none
TEST=emerge-volteer -j vboot_reference
     "lddtree /build/volteer/usr/bin/futility" lists libcrosid

Cq-Depend: chromium:3367251
Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Change-Id: I8e69c5ce4570ac9df72440d0a34b6b03b5a36e77
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3368703
Reviewed-by: Raul Rangel <9a9c998e11a2655b1de9a05eeeef5f710c0dc7ed@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot