Add attribute 'Object_File_Prefix' for package Compiler

[SergeyNM]

Good day!

For examples, output names with prefix use in moc, uic, rcc compilers: https://doc.qt.io/qt-6/moc.html
It is the initial commit. I will be very glad to see your comments.

-- Prototype of project file

project UIC is
   --  Qt User Interface Compiler
   for Languages use ("UIC");
   for Source_Dirs use ("Src");
   for Object_Dir use "Release";

   for Objects_Linked ("UIC") use "False";

   package Naming is
      for Body_Suffix ("uic") use ".ui";
   end Naming;

   package Compiler is
      for Driver ("UIC") use "/usr/lib/qt5/bin/uic";
      for Object_File_Suffix ("UIC") use ".h";
      for Object_File_Prefix ("UIC") use "ui_";
      for Object_File_Switches ("UIC") use ("-o", "");
   end Compiler;
end UIC;

--

-- output
./gprbuild -vm /home/user_1/Projects/Qt_Examples/Test_1/uic.gpr
GPRBUILD Pro 18.0w (19940713) (x86_64-pc-linux-gnu)
Copyright (C) 2004-2016, AdaCore
24 lines: No errors
TMPDIR = "/tmp"
gprconfig --batch -o /tmp/GNAT-TEMP-000001.TMP --target=x86_64-pc-linux-gnu --fallback-targets --config=uic,,,,
Error: unknown language 'uic'
Checking configuration /tmp/GNAT-TEMP-000001.TMP
Setting the default project search directories
Adding directory "/usr/lib/qt5/x86_64-pc-linux-gnu/share/gpr"
Adding directory "/usr/lib/qt5/x86_64-pc-linux-gnu/lib/gnat"
Adding directory "/usr/lib/qt5/x86_64-linux/share/gpr"
Adding directory "/usr/lib/qt5/x86_64-linux/lib/gnat"
Adding directory "/usr/lib/qt5/share/gpr"
Adding directory "/usr/lib/qt5/lib/gnat"
gprconfig --batch -o /tmp/GNAT-TEMP-000002.TMP --target=x86_64-pc-linux-gnu --fallback-targets --config=uic,,,,
Error: unknown language 'uic'
Checking configuration /tmp/GNAT-TEMP-000002.TMP
Setting the default project search directories
Adding directory "/usr/lib/qt5/x86_64-pc-linux-gnu/share/gpr"
Adding directory "/usr/lib/qt5/x86_64-pc-linux-gnu/lib/gnat"
Adding directory "/usr/lib/qt5/x86_64-linux/share/gpr"
Adding directory "/usr/lib/qt5/x86_64-linux/lib/gnat"
Adding directory "/usr/lib/qt5/share/gpr"
Adding directory "/usr/lib/qt5/lib/gnat"
Checking /home/user_1/Projects/Qt_Examples/Test_1/Src/mainwindow.ui ...
-> object file /home/user_1/Projects/Qt_Examples/Test_1/Release/ui_mainwindow.h does not exist
Changing to object directory of "UIC": "/home/user_1/Projects/Qt_Examples/Test_1/Release/"
/usr/lib/qt5/bin/uic /home/user_1/Projects/Qt_Examples/Test_1/Src/mainwindow.ui -o ui_mainwindow.h

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