RFR: JDK-8266797: Fix for 8266610 breaks the build on macos

[Alan Bateman]

On Mon, 10 May 2021 10:31:40 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> No, change is specific to Linux. Please see(https://github.com/openjdk/jdk/commit/69b96f9a1b4a959c6b86f41c2259d9e4d47c8ede).
>
> OK, so what you are saying is that the path that references `S_ISBLK` is protected by `BLKGETSIZE64` that is guaranteed to be undefined on OS X? If so, this is (awkwardly) fine.

I think Vymon took the code from FileDispatcherImpl_size0, which has been compiling on macOS without issues. I don't mind if we fix the issue with this PR or just back it out and fix it with another PR.

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PR: https://git.openjdk.java.net/jdk/pull/3943