fix libigl links not found (#4952)

packages/l/libigl/xmake.lua

@@ -26,7 +26,9 @@ package("libigl")
 
     add_deps("cmake", "eigen")
     on_load("macosx", "linux", "windows", "mingw", function (package)
-        if not package:config("header_only") then
+        if package:config("header_only") then
+            package:set("kind", "library", {headeronly = true})
+        else
             raise("Non-header-only version is not supported yet!")
         end
         if package:config("cgal") then