RFR: 8252191: Update to gcc 10.2 on Linux

[Johan Vos]

On Tue, 29 Sep 2020 23:34:55 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> This patch updates the compiler to gcc 10.2 on Linux, in order to match JDK 16 -- see
> [JDK-8253616](https://bugs.openjdk.java.net/browse/JDK-8253616).
> I ran a full build and test, including media and WebKit.

Marked as reviewed by jvos (Reviewer).

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PR: https://git.openjdk.java.net/jfx/pull/311