RFR: 8258534: Epsilon: clean up unused includes

[Tintin]

On Fri, 11 Dec 2020 17:28:24 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Hi all,
>> 
>> CLion IDE shows two warnings of unused includes(`#include "utilities/macros.hpp"`) in EpsilonGC's code. these maybe can be removed.
>> 
>> Testing: macosx-x86_64-server-{release,fastdebug,slowdebug}
>
> Unfortunately, CLion makes the incorrect call here. `macros.hpp` is included to get access to `COMPILER1` and `COMPILER2` macros. So we cannot really remove that `#include`.

Thank you for your review. When the CLion shows the two warnings, I try to found `COMPILER1` and `COMPILER2` macros define from `utilities/macros.hpp` file but can not. Or the two macros be added to `utilities/macros.hpp` file when building? My understanding is that the two macros come from `C_FLAGS`(`-DCOMPILER1`, `-DCOMPILER2`) when building.

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PR: https://git.openjdk.java.net/jdk/pull/1745