Resolution: Out of scope
If qt4 is integrated into other projects, in my case, Yocto, it's likely that the 256 length limit of its building path is not enough. [Our building directory usually contain information about date, architecture, branch and so on. Our it's easy exceed 100 chars. Sometimes it reaches over 256 chars.]
In its configure file, there are statements like below:
-static const char qt_configure_prefix_path_str [256 + 12] = "$PREFIX_PATH_STR";
-static const char qt_configure_documentation_path_str[256 + 12] = "$DOCUMENTATION_PATH_STR";
-static const char qt_configure_headers_path_str [256 + 12] = "$HEADERS_PATH_STR";
-static const char qt_configure_libraries_path_str [256 + 12] = "$LIBRARIES_PATH_STR";
-static const char qt_configure_binaries_path_str [256 + 12] = "$BINARIES_PATH_STR";
I suggest replace 256 by 512. I think 512 is a reasonable value for practical use.
Attached is a raw patch I worked out. Please have a look at it. Thanks.