* fix FindLZ4 to follow convention (LIBRARIES, not LIBRARY)
* remove redundant checks from rocksdb/CMakeLists.txt
* put all checks through the same macro that uniformly
checks for a package, prints the message, adds definition
The library finder needs to have capitals in its name so that FIND_PACKAGE
will load the correct finder and actually detect that libzstd is available.
Without this change the CMake would just always silently skip ZSTD since
it would never find it.
Simplify Debian autopkgtest RocksDB part and make it more verbose so that
future regressions like this are easier to debug.
Also remove QUIET from the RocksDB FIND_PACKAGE call so that it is easier
to read in build logs what libraries were detected. Also add missing
underscores to error messages.
This change add WITH_ROCKSDB_{LZ4,BZIP2,ZSTD,snappy} CMake variables
that can be set to ON/OFF/AUTO.
If variable has default value AUTO, rocksdb links with corresponding
compression library. OFF disables compiling/linking with specific compression
library, ON forces compiling with it (cmake would throw error if library
is not available)
Support for ZLIB is added unconditionally, as it is always there.
