add pkgconfig sources

Co-authored-by: Copilot <copilot@github.com>

Author: xq114

packages/g/glu/xmake.lua

@@ -11,7 +11,7 @@ package("glu")
         end
         if opt.system then
             if package:is_plat("linux") and package.find_package then
-                return package:find_package("GLU", opt)
+                return package:find_package("GLU", opt) or package:find_package("pkgconfig::libglu", opt)
             end
         end
     end)

packages/g/glx/xmake.lua

@@ -6,7 +6,7 @@ package("glx")
     on_fetch(function (package, opt)
         if opt.system then
             if package:is_plat("linux") and package.find_package then
-                return package:find_package("GLX", opt)
+                return package:find_package("GLX", opt) or package:find_package("pkgconfig::libglx", opt)
             end
         end
     end)

packages/o/opengl/xmake.lua

@@ -12,7 +12,7 @@ package("opengl")
         end
         if opt.system then
             if package:is_plat("linux") and package.find_package then
-                return package:find_package("OpenGL", opt) or package:find_package("GL", opt)
+                return package:find_package("OpenGL", opt) or package:find_package("GL", opt) or package:find_package("pkgconfig::libopengl", opt) or package:find_package("pkgconfig::libgl", opt)
             end
         end
     end)