Fix the host_bins variable in the QtCore pkg-config file

The qmake HOST_BINS property has no /raw variant. We need to use the
regular one.

Change-Id: I38254f77d1039c312913a987353342ce5ed3feec
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Support setting the library-search environment on a few more OSs

Most Unix systems will honor LD_LIBRARY_PATH (all ELF-based systems
definitely do), so let's not make it an error if the user isn't
compiling on Linux or FreeBSD. The only known exception are Darwin /
Mac OS X and AIX. For everything else, cause an error.

The list of unames came from: http://en.wikipedia.org/wiki/Uname.

AIX does not use ELF, so its variable is called LIBPATH:
 http://publib.boulder.ibm.com/infocenter/forms/v3r5m0/index.jsp?topic=/com.ibm.form.api.configuring.doc/api_configuring_unix_path.html

Change-Id: I67055e6a231aa1430d91431e7cab5f98f0e1bd95
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>