RFR: 8313576: GCC 7 reports compiler warning in bundled freetype 2.13.0

[Sergey Bylokhov]

One warning is disabled for the freetype.

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Commit messages:
 - 8313576: GCC 7 reports some compiler warnings in bundled freetype 2.13.0

Changes: https://git.openjdk.org/jdk/pull/15116/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15116&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313576
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15116.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15116/head:pull/15116

PR: https://git.openjdk.org/jdk/pull/15116