Fix tests with code coverage enabled

Author: staticfloat

src/codegen/forward_demand.jl

@@ -183,6 +183,8 @@ function forward_visit!(ir::IRCode, ssa::SSAValue, order::Int, ssa_orders::Vecto
         foreach(recurse, stmt.args)
     elseif isa(stmt, SSAValue)
         recurse(stmt)
+    elseif isexpr(stmt, :code_coverage_effect)
+        return
     elseif !isa(stmt, Expr)
         return
     else