[PyQt] Incorrect Makefile using .prl files from Qt 5.12.4

[Hans Gaiser]

Hi there,

Since Qt 5.12.4, .prl files use $$[QT_INSTALL_LIBS] variables to 
indicate the absolute location in which Qt libraries are installed. In 
Qt 5.12.3:

cat /usr/lib/libQt5Gui.prl

...
QMAKE_PRL_LIBS =  -lQt5Core -lpthread

However, in Qt 5.12.4:

cat /usr/lib/libQt5Gui.prl

...
QMAKE_PRL_LIBS = $$[QT_INSTALL_LIBS]/libQt5Core.so -lpthread

These variables are not substituted by sip. The package I am using, uses 
sip to generate a Makefile. Because of this issue, in my Makefile I have 
an entry along the lines of:

LFLAGS = <....removed for clarity....> -lQt5Core -lpthread -lQt5Gui 
$$[QT_INSTALL_LIBS]/libQt5Core.so

This LFLAG causes failure during compilation. Should sip parse these 
variables, or should these variables not be in .prl files in the first 
place (in which case it is an upstream issue)?

Best regards,

Hans