[platform] Work around potentially missing `madvise()`

Some Linux kernels are built without `madvise()`. In that
case, do not crash but rather ignore the return value instead.

Refs: https://github.com/nodejs/node/issues/21562
Change-Id: Iff8d0d0e9e7935804e2fc994be7f8bd21c553846
Reviewed-on: https://chromium-review.googlesource.com/1131943Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54415}

src/base/platform/platform-posix.cc

@@ -156,6 +156,8 @@ int ReclaimInaccessibleMemory(void* address, size_t size) {
 #else
   int ret = madvise(address, size, MADV_FREE);
 #endif
+  if (ret != 0 && errno == ENOSYS)
+    return 0;  // madvise is not available on all systems.
   if (ret != 0 && errno == EINVAL) {
     // MADV_FREE only works on Linux 4.5+ . If request failed, retry with older
     // MADV_DONTNEED . Note that MADV_FREE being defined at compile time doesn't