I'm having a similar problem with the auto installer for Linux 64. The installer gets about half way and then stops with the error message:
Error during installation process (qt.54.gcc_64):
File '/qt/5.4/gcc_64/bin/qmake' does not exist or is not an executable binary.
Checked the files and sure enough qmake is not executable by any user and only read write by root, I tried chmod but can't make the file executable. I don't really understand why its not working I have a working tool-chain and executing the run file as root.
I haven’t tried building it from source yet, just hoping some one might know what’s happening?