Use BB-like EBB in docs/*.clif

cranelift/docs/callex.clif

@@ -4,10 +4,13 @@ function %gcd(i32 uext, i32 uext) -> i32 uext system_v {
     fn0 = %divmod(i32 uext, i32 uext) -> i32 uext, i32 uext
 
 ebb1(v0: i32, v1: i32):
-    brz v1, ebb2
+    brz v1, ebb3
+    jump ebb2
+
+ebb2:
     v2, v3 = call fn0(v0, v1)
     return v2
 
-ebb2:
+ebb3:
     return v0
 }