About the external project of sdbusplus in bmcweb

[Lei YU]

While I was adding some new function in sdbusplus, it's found that bmcweb is
not working correctly, that it always gives errors like below.

    Jun 11 09:14:26 romulus bmcweb[1501]: terminate called after
throwing an instance of 'sdbusplus::exception::SdBusError'
    Jun 11 09:14:26 romulus bmcweb[1501]:   what():  sd_bus_process
discard: org.freedesktop.DBus.Error.AccessDenied: Operation not
permitted

Then it's noticed that bmcweb is using its own revision of sdbusplus during
build, as external project in "CMakeLists.txt.in"

It's worrying that one should expect that the whole build of OpenBMC should
use a single sdbusplus lib defined in
meta-phosphor/recipes-extended/sdbusplus/sdbusplus_git.bb, but apparently
it's not for bmcweb, and that results in the weird behavior.

When I change the "CMakeLists.txt.in" to use the same revision as the one in
sdbusplus_git.bb, the issue is gone and bmcweb behaves normally.

So the question is, why bmcweb uses sdbusplus this way? Is it possible to make
it just link against sdbusplus like other repos?

Thanks!