Link Time Optimization with gcc can be faster

A previous argument against link time optimization support that we have for gcc is that it was extremely slow. After some checks it turns out we are passing rather inefficient flags to gcc in optimized builds. Changing these flags to run the linker optimizations in parallel and passing additional flags to the compiler have the ability to speed this process up significantly. Also fixes some incorrect flags passed to ld for linking as well, since strict-aliasing is required for both linker and compiler, and the same optimization level should be specified instead of letting the default -O1 be passed to the linker