[jdk21u-dev] RFR: 8316893: Compile without -fno-delete-null-pointer-checks

[SendaoYan]

Hi all,
There are some gcc compile warnings which recorded by [JDK-8342304](https://bugs.openjdk.org/browse/JDK-8342304) on linux-riscv64 platform, and the PR [JDK-8316893](https://bugs.openjdk.org/browse/JDK-8316893) fix the gcc compile warnings. So I want to backport [JDK-8316893](https://bugs.openjdk.org/browse/JDK-8316893) to jdk21u-dev.

Additional testing:

- [ ] 1. jtreg tests(include tier1/2/3 etc.) with linux-x64 release build
- [ ] 2. jtreg tests(include tier1/2/3 etc.) with linux-x64 fastdebug build
- [ ] 3. jtreg tests(include tier1/2/3 etc.) with linux-aarch64 release build
- [ ] 4. jtreg tests(include tier1/2/3 etc.) with linux-aarch64 fastdebug build

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Commit messages:
 - Backport 287b24322135b54641f013970c4545ce069c4350

Changes: https://git.openjdk.org/jdk21u-dev/pull/1178/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1178&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316893
  Stats: 17 lines in 1 file changed: 0 ins; 14 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1178.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1178/head:pull/1178

PR: https://git.openjdk.org/jdk21u-dev/pull/1178