mkqt5bld: Replace rpath only for Linux Desktop builds

When cross-compiling for QNX x86 or armv7 on a Linux x64 host the
.so files don't get patched even if you use a 32-bit chrpath on
the 64-bit host.

This change removes the need to even try to patch cross-compiled
builds such as Android and QNX on a Linux host.

Change-Id: I538c1c79ef91c62ece2ec660b5c29602032f14eb
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
build_wrapper: Remove --replace-rpath option for Android and QNX

This option does not have any effect when doing cross-compiled
builds for Android and QNX on Linux, so removing it.

Change-Id: I397f508354c5d75dbde99634cea0feeb16bb12a3
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>