RFR: 8366225: Linux Alpine (fast)debug build fails after JDK-8365909

[Manuel Hässig]

The integration of #26882 broke debug builds on Alpine Linux (and probably other distributions using musl libc), because the typedef `sigevent_t`does not exist in musl libc. This PR fixes this by using `struct sigevent` as the type.

Testing:
 - [ ] Github Actions
 - [ ] tier1,tier2 Linux aarch64 and x64 fastdebug
 - [x] `make test TEST=compiler/arguments/TestCompileTaskTimeout.java` in Alpine Linux docker container 
 - [ ] tier1,tier2 on Alpine Linux fastdebug

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Commit messages:
 - Fix alpine build

Changes: https://git.openjdk.org/jdk/pull/26956/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26956&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366225
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26956.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26956/head:pull/26956

PR: https://git.openjdk.org/jdk/pull/26956