MESA: TestPBRLighting/reflective shader node broken

On Discord we got an error report about PBRLight being broken and there also was a forum post from nehon back then.
Basically the problem is that shader nodes go wrong quite a bit, specifically it does not include GLSLCompat.glsllib but instead manually replicates a few things, this could be part of the problem.

Also the language seems to be GLSL100 whereas #version 110 is defined in the compiled shader.
For some reason MESA stills doesn't accept textureCubeLod, which seems to be gone or renamed only in versions PAST 110.

Apr 06, 2020 4:20:03 PM com.jme3.app.LegacyApplication handleError
SEVERE: Uncaught exception thrown in Thread[jME3 Main,6,main]
com.jme3.renderer.RendererException: compile error in: ShaderSource[name=Default.frag, defines, type=Fragment, language=GLSL100]
0:28(21): error: no function with name 'textureCubeLod'

        at com.jme3.renderer.opengl.GLRenderer.updateShaderSourceData(GLRenderer.java:1498)
        at com.jme3.renderer.opengl.GLRenderer.updateShaderData(GLRenderer.java:1525)
        at com.jme3.renderer.opengl.GLRenderer.setShader(GLRenderer.java:1590)
        at com.jme3.material.logic.DefaultTechniqueDefLogic.render(DefaultTechniqueDefLogic.java:94)
        at com.jme3.material.Technique.render(Technique.java:166)
        at com.jme3.material.Material.render(Material.java:1028)
        at com.jme3.renderer.RenderManager.renderGeometry(RenderManager.java:614)
        at com.jme3.renderer.queue.RenderQueue.renderGeometryList(RenderQueue.java:266)
        at com.jme3.renderer.queue.RenderQueue.renderQueue(RenderQueue.java:305)
        at com.jme3.renderer.RenderManager.renderViewPortQueues(RenderManager.java:877)
        at com.jme3.renderer.RenderManager.flushQueue(RenderManager.java:779)
        at com.jme3.renderer.RenderManager.renderViewPort(RenderManager.java:1108)
        at com.jme3.renderer.RenderManager.render(RenderManager.java:1158)
        at com.jme3.app.SimpleApplication.update(SimpleApplication.java:273)
        at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:157)
        at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:196)
        at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:239)
        at java.base/java.lang.Thread.run(Thread.java:834)

The report points to TestPBRLighting and the Default.frag shader compilation path; start by reproducing the Mesa error and tracing how GLSL100 is assembled, including GLSLCompat.glsllib and textureCubeLod. Done means the reflective/PBR shader compiles and renders under Mesa without the reported error.