Already defined in Mga8+:

/home/iurt/rpmbuild/BUILD/VirtualBox-6.0.10/include/VBox/VBoxGL2D.h:116:19: error: conflicting declaration 'typedef ptrdiff_t GLsizeiptr'
 typedef ptrdiff_t GLsizeiptr;
                   ^~~~~~~~~~
In file included from /usr/lib/qt5/include/QtGui/qopengl.h:146,
                 from /usr/lib/qt5/include/QtOpenGL/qgl.h:45,
                 from /usr/lib/qt5/include/QtOpenGL/QGLWidget:1,
                 from /home/iurt/rpmbuild/BUILD/VirtualBox-6.0.10/src/VBox/Frontends/VirtualBox/src/VBoxGLSupportInfo.cpp:22:
/usr/lib/qt5/include/QtGui/qopenglext.h:475:30: note: previous declaration as 'typedef long int GLsizeiptr'
 typedef signed long int      GLsizeiptr;

diff -Nurp VirtualBox-6.0.10.orig/include/VBox/VBoxGL2D.h VirtualBox-6.0.10/include/VBox/VBoxGL2D.h
--- VirtualBox-6.0.10.orig/include/VBox/VBoxGL2D.h	2019-07-12 11:28:22.000000000 +0300
+++ VirtualBox-6.0.10/include/VBox/VBoxGL2D.h	2019-07-20 21:13:31.481755822 +0300
@@ -110,12 +110,6 @@ typedef GLvoid (APIENTRY *PFNVBOXVHWA_UN
 typedef GLvoid (APIENTRY *PFNVBOXVHWA_UNIFORM3I)(GLint location, GLint v0, GLint v1, GLint v2);
 typedef GLvoid (APIENTRY *PFNVBOXVHWA_UNIFORM4I)(GLint location, GLint v0, GLint v1, GLint v2, GLint v3);
 
-/* GL_ARB_pixel_buffer_object*/
-#ifndef Q_WS_MAC
-/* apears to be defined on mac */
-typedef ptrdiff_t GLsizeiptr;
-#endif
-
 #ifndef GL_READ_ONLY
 # define GL_READ_ONLY                   0x88B8
 #endif