Compile snappy in lib folder.

Currently libsnappy is being compiled in the folder lib64 in some
OSes (e.g. SUSE SLE 15.6).
This is a problem because some dependents look for the library in the
lib subdirectory.
This change forces snappy to always use the lib directory.

See merge request nexedi/slapos!1581

component/snappy/buildout.cfg

@@ -14,3 +14,4 @@ configure-options =
   -DCMAKE_BUILD_TYPE=Release
   -DCMAKE_INSTALL_PREFIX=@@LOCATION@@
   -DBUILD_SHARED_LIBS=ON
+  -DCMAKE_INSTALL_LIBDIR=lib