mesa-21.3.8 error

[naiquan]

When building 7.0, we get an error:
"kBuild: Generating flex - C:/VBoxBuild/VirtualBox/out/win.amd64/release/obj/VBoxMesaLib/mesa-21.3.8/src/compiler/glsl/glsl_lexer.cpp
flex.exe: can't open C:/VBoxBuild/VirtualBox/out/win.amd64/release/obj/VBoxMesaLib/mesa-21.3.8/src/compiler/glsl/glsl_lexer.cpp
kmk: *** [C:/VBoxBuild/VirtualBox/src/VBox/Additions/3D/mesa/Makefile.kmk:500: C:/VBoxBuild/VirtualBox/out/win.amd64/release/obj/VBoxMesaLib/mesa-21.3.8/src/compiler/glsl/glsl_lexer.cpp] Error 1 (0x1)"

Could not generate the glsl lexer.cpp file, resulting in a compilation error