fix runtime error on alpha while jemalloc run

The define for 'pagesize_2pow' isn't correctly set for the alpha
platform so the runtime jemalloc compiler was running into a error.
disable optimization on alpha while linking

The linker option '-Wl,--no-keep-memory' doesn't work well on alpha,
also optimization isn't working propably.
More infos on this in the bug report #650151 post 40.
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=650151#40