how to compile webgl and webgpu into the same package

i wrote an rendering engine with webgl as the backend , now add webgpu as an optional backend. How do I compile both graphic api to the same js pakage with compiler directive, I tried, but only one graphic interface worked, when i build webgpu package, the webgl will not work , the prompt is that "GL is not defined"...
Anybody give me some help? Thanks!