PerconaFT does not pass cmake flags on to snappy cmake

CMake does not pass on the CMAKE_AR, CMAKE_NM and CMAKE_RANLIB flags when building Snappy. This results in warnings when building MariaDB with LTO enabled, I imagine this might also cause problems with cross-compiling.

Linking CXX static library libsnappy.a
BFD: CMakeFiles/snappy.dir/snappy.o: plugin needed to handle lto object
BFD: CMakeFiles/snappy.dir/snappy-c.o: plugin needed to handle lto object
BFD: CMakeFiles/snappy.dir/snappy-sinksource.o: plugin needed to handle lto object
BFD: CMakeFiles/snappy.dir/snappy-stubs-internal.o: plugin needed to handle lto object
BFD: snappy.o: plugin needed to handle lto object
BFD: snappy-c.o: plugin needed to handle lto object
BFD: snappy-sinksource.o: plugin needed to handle lto object
BFD: snappy-stubs-internal.o: plugin needed to handle lto object
[100%] Built target snappy

Suggested patch: https://jira.mariadb.org/secure/attachment/42845/fix-snappy-lto-build.patch

This was originally reported as https://jira.mariadb.org/browse/MDEV-11211