Cross compilation issue: strip detection

[egavrin]

There is one minor issue leftover: If we cross-compile to x86_64 then it is possible that the line

find_program(CMAKE_STRIP NAMES x86_64-linux-gnu-strip x86_64-unknown-linux-gnu-strip strip)

in the build/configs/toolchain_linux_x86_64.cmake file would make the CMAKE_STRIP to use the
default strip binary, which could be incorrect for the given target, as the strip would be for the host.

Reported by @galpeter in comments to #71

[egavrin]

Regular strip can be removed from config, native or cross compilers should provide x86_64-linux-gnu-strip links.

Can be fixed within #206

[galpeter]

Regular strip can be removed from config, native or cross compilers should provide x86_64-linux-gnu-strip links.

That's maybe true for cross compilers, but not true for native compilers. For example on my system the native compiler gives just the strip.