build: find ncurses headers and the 32-bit ncurses lib on Arch

CMake 4.4's FindCurses leaves CURSES_HAVE_* unset on this system, so the
HAVE_CURSES_H fallback keeps viocalls compiling. Also fall back to
/usr/lib32/libncursesw.so.6 when the hard-coded Debian path is absent.

CMakeLists.txt

@@ -69,6 +69,8 @@ elseif(CURSES_HAVE_CURSES_H)
     add_definitions(-DHAVE_CURSES_H)
 elseif(CURSES_HAVE_NCURSES_CURSES_H)
     add_definitions(-DHAVE_NCURSESW_NCURSES_H)
+else()
+    add_definitions(-DHAVE_CURSES_H)
 endif()
 
 # !!! FIXME
@@ -97,7 +99,11 @@ endforeach()
 
 target_link_libraries(doscalls "pthread")
 # FIXME target_link_libraries(viocalls ${CURSES_LIBRARIES})
-target_link_libraries(viocalls /usr/lib/i386-linux-gnu/libncursesw.so.6)
+if(EXISTS "/usr/lib/i386-linux-gnu/libncursesw.so.6")
+    target_link_libraries(viocalls /usr/lib/i386-linux-gnu/libncursesw.so.6)
+else()
+    target_link_libraries(viocalls /usr/lib32/libncursesw.so.6)
+endif()
 
 # !!! FIXME: clean this up/
 if(LX_LEGACY)