[oe] Installing RPM packages in SDK sysroot

[Adam Lee]

Hello everyone, in the section 4.2. Configuring the PMS of the Yocto ADT
manual, it describes adding packages to a target sysroot using OPKG. This
method works well as documented. However my choice of package manager is
Yocto's default - RPM. And I was not able to successfully install RPM
packages in the SDK sysroot.

Ultimately, I think installing RPM packages using SmartPM fails because the
list of installed packages is not included in the SDK sysroot. A deployable
image contains a file called Packages in /var/lib/rpm. The SDK sysroot does
not have this file and shows 0 installed packages when I run `smart stats`.
Note that when I am using OPKG instead of RPM, I have the equivalent
package index file in /var/lib/opkg/lists for both sysroot and deployable
images.

I can still attempt to install a package, but it quite literally wants to
rebuild the entire rootfs. For example, running `smart install opencv-dev`
warns that it has to install 400 packages. These packages include
base-files, bash, m4, make, python-dev etc.

So this makes me think that either RPM is not supported in SDK sysroot or
the feature is incomplete. It's also possible that I have missed an
important detail.

I will be looking into the sdk class and the package manager class to see
what's really happening. In the meanwhile I'd appreciate if someone can
provide some pointers!

Thanks,

Adam