Paths in libQt5*.la files are broken

Step to reproduce this bug:

1. Install Qt to the default directory with the Qt Online Installer for Linux (64-bit).
2. Check the content of /home/hebasto/Qt/5.12.0/gcc_64/lib/libQt5*.la files:

$ cat /home/hebasto/Qt/5.12.0/gcc_64/lib/libQt5Gui.la | grep '=/'
dependency_libs='-L=/home/hebasto/Qt/5.12.0/gcc_64/lib -lQt5Core -lpthread  '
libdir='=/home/hebasto/Qt/5.12.0/gcc_64/lib'

There is an unexpected '=' character preceding path strings.