package/libsolv: new package

Required by micromamba.

Signed-off-by: TIAN Yuanhao <tianyuanhao3@163.com>
[Thomas:
 - rework shared/static lib handling
 - don't pass ENABLE_CONDA=ON based on BR2_PACKAGE_MICROMAMBA=y as
   it's weird that a dependency does something different depending on
   which of its reverse dependencies is enabled]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>