[jdk17u-dev] RFR: 8289512: Fix GCC 12 warnings for adlc output_c.cpp

[Ben Taylor]

Backport is clean, required to build with GCC 13

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Commit messages:
 - Backport a8fe2d97a2ea1d3ce70d6095740c4ac7ec113761

Changes: https://git.openjdk.org/jdk17u-dev/pull/1574/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1574&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289512
  Stats: 13 lines in 1 file changed: 1 ins; 3 del; 9 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1574.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1574/head:pull/1574

PR: https://git.openjdk.org/jdk17u-dev/pull/1574