Creating Xcode project from .pro file using qmake will not quote certain strings in Xcode project, causing build errors.

Using qmake to build an Xcode project file from a QT project file doesn't quote some file paths in the Xcode project.pbxproj file, causing build errors in Xcode if the path to the file has spaces in it (e.g. "/Users/user/Documents/QT Projects/test").

Steps to reproduce:
1. Create a new QT project.
2. Use qmake to create an Xcode project file.
3. Open the project in Xcode and try to compile.

The following errors are produced:
Make: test.xcodeproj/qt_makeqmake.mak: No such file or directory
Make: test.xcodeproj/qt_preprocess.mak: No such file or directory

Workaround:
1. Locate the xcodeproj file created from the qmake process.
2. Show its contents (Show Package Contents).
3. Open project.pxproj in a text editor.
4. Search for "qt_preprocess.mak" and "qt_makeqmake.mak".

Something like the following lines should be found:

shellScript = "make -C /Users/user/Documents/QT Projects/test -f 'test.xcodeproj/qt_preprocess.mak'";

shellScript = "make -C /Users/user/Documents/QT Projects/test -f 'test.xcodeproj/qt_makeqmake.mak'";

Add quotes around the paths so that they become '/Users/user/Documents/Qt Projects/test'.

5. The project should now compile.