qmake: add page (#15507)

* Create qmake.md

* Update pages/linux/qmake.md

Co-authored-by: cyqsimon <28627918+cyqsimon@users.noreply.github.com>

* Update qmake.md

---------

Co-authored-by: cyqsimon <28627918+cyqsimon@users.noreply.github.com>

pages/linux/qmake.md

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+# qmake
+
+> Generate Makefiles from Qt project files.
+> More information: <https://doc.qt.io/qt-6/qmake-manual.html>.
+
+- Generate a `Makefile` from a project file in the current directory:
+
+`qmake`
+
+- Specify `Makefile` and project file locations:
+
+`qmake -o {{path/to/Makefile}} {{path/to/project_file.pro}}`
+
+- Generate a default project file:
+
+`qmake -project`
+
+- Compile a project:
+
+`qmake && make`
+
+- Enable debug mode:
+
+`qmake -d`