RFR: JDK-8274283: string-concatenation build warning as error with clang 13 on macOS aarch64

[Matthias Baesken]

Please review this small fix fixing builds using clang 13.
We run into this error when compiling with clang version 13.0.0 (clang-1300.0.29.3) :

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Commit messages:
 - JDK-8274283

Changes: https://git.openjdk.java.net/jdk/pull/5680/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5680&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274283
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5680.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5680/head:pull/5680

PR: https://git.openjdk.java.net/jdk/pull/5680