vc4: Print live variable start/ends during QIR dumping.
vc4: Print live variable start/ends during QIR dumping.

This only happens when live variables are set up, which is not in the
normal dump, but is set up when we've failed to register allocate.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler