debuginfo: store location of loop boundary (#41857)

Since lowering always inserts gotos and other instructions after loop
bodies, this allows debuggers to give a more useful location for these
instructions.

fixes JuliaDebug/JuliaInterpreter.jl#485

src/macros.jl

@@ -347,6 +347,9 @@ macro distributed(args...)
     var = loop.args[1].args[1]
     r = loop.args[1].args[2]
     body = loop.args[2]
+    if Meta.isexpr(body, :block) && body.args[end] isa LineNumberNode
+        resize!(body.args, length(body.args) - 1)
+    end
     if na==1
         syncvar = esc(Base.sync_varname)
         return quote