Reland "[nojit] Don't flush the icache in jitless mode"

This is a reland of 71d29f78

Original change's description:
> [nojit] Don't flush the icache in jitless mode
> 
> We don't allocate executable memory in jitless mode hence there's no
> need to flush the icache.
> 
> Bug: v8:7777
> Change-Id: I70a1884e6c9f11405465f5741f2eccd4f7a273fb
> Reviewed-on: https://chromium-review.googlesource.com/c/1488765
> Commit-Queue: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59887}

Bug: v8:7777
Change-Id: Id48455cf4e6d28ad2a0b753580ca51cbe0e983d3
Reviewed-on: https://chromium-review.googlesource.com/c/1491601Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59916}

src/flush-instruction-cache.cc

@@ -13,6 +13,7 @@ namespace internal {
 
 void FlushInstructionCache(void* start, size_t size) {
   if (size == 0) return;
+  if (FLAG_jitless) return;
 
 #if defined(USE_SIMULATOR)
   base::MutexGuard lock_guard(Simulator::i_cache_mutex());

test/cctest/cctest.status

@@ -574,6 +574,9 @@
 
   # Field representation tracking is disabled in jitless mode.
   'test-field-type-tracking/*': [SKIP],
+
+  # Instruction cache flushing is disabled in jitless mode.
+  'test-icache/*': [SKIP],
 }], # lite_mode or variant == jitless
 
 ##############################################################################