boost: define required dependency

Latest upstream yocto is failing due to being unable to find the boost
header files. Define the needed dependency.

This will require a DEPENDS update in phosphor-power_git.bb before it
will build:
https://gerrit.openbmc-project.xyz/c/openbmc/meta-phosphor/+/33014

Tested:
Verified with the corresponding recipe change that phosphor-power now
builds against upstream yocto

Change-Id: I382fae08ed2a525f39d1873ee1a2719fa85d9964
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/meson.build b/meson.build
index 58e57de..d3312f4 100644
--- a/meson.build
+++ b/meson.build
@@ -39,6 +39,7 @@
 sdeventplus = dependency('sdeventplus')
 pthread = dependency('threads')
 stdplus = dependency('stdplus')
+boost = dependency('boost')
 
 systemd = dependency('systemd')
 servicedir = systemd.get_pkgconfig_variable('systemdsystemunitdir')