[X] Add zlib dependency
[ ] Static libraries should not be installed with execute permissions.
    "fltk.list" has entires with 444 permissions, looks like a bug.
[ ] Check for library suffixes on HP-UX and macOS
[ ] Some configurations create the compiler warnings below.

drivers/Xlib/Fl_Xlib_Graphics_Driver_font_x.cxx: In member function 'virtual const char* Fl_Xlib_Graphics_Driver::get_font_name(Fl_Font, int*)':
drivers/Xlib/Fl_Xlib_Graphics_Driver_font_x.cxx:140:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
         if (*e) e++; x = e; e = fl_font_word(x,1);
         ^~
drivers/Xlib/Fl_Xlib_Graphics_Driver_font_x.cxx:140:22: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
         if (*e) e++; x = e; e = fl_font_word(x,1);
                      ^
