[jdk8u-dev] RFR: 8074840: Resolve disabled warnings for libjli and libjli_static

[Zdenek Zambersky]

Backport, which fixes compiler errors/warnings in libjli.

**Motivation:**
- to fix compilation error (and some warnings) on macos-15 (clang):

...
2025-11-19T17:50:19.3284070Z /Users/runner/work/jdk8u-dev/jdk8u-dev/jdk/jdk/src/share/bin/parse_manifest.c:680:12: note: use '==' to turn this assignment into an equality comparison
2025-11-19T17:50:19.3285850Z   680 |     if (rc = find_file(fd, &entry, manifest_name) != 0) {
2025-11-19T17:50:19.3286370Z       |            ^
2025-11-19T17:50:19.3287050Z       |            ==
2025-11-19T17:50:19.3287530Z 4 warnings generated.
2025-11-19T17:50:19.3289930Z /Users/runner/work/jdk8u-dev/jdk8u-dev/jdk/jdk/src/share/bin/splashscreen_stubs.c:64:30: error: incompatible pointer to integer conversion returning 'void *' from a function with result type 'int' [-Wint-conversion]
2025-11-19T17:50:19.3291940Z    64 |     INVOKE(SplashLoadMemory, NULL)(pdata, size);
2025-11-19T17:50:19.3292900Z       |                              ^~~~
...


**Differences in 8:**
- excluded changes in `jdk/make/lib/CoreLibraries.gmk` due to differences in build system (not applicable to 8)
- excluded cast of `STACK_SIZE_MINIMUM` in `java.c`, as [JDK-6762191](https://bugs.openjdk.org/browse/JDK-6762191), which adds that code, is missing in 8
- excluded modifications to `readAt` function in `parse_manifest.c`, as function was added by [JDK-8073158](https://bugs.openjdk.org/browse/JDK-8073158), which is missing in 8
- copyright differences due to missing backports or backport applied out of order (some had to be updated manually)
- differences in paths

Apart from above differences most of remaining code changes applied cleanly (with updated paths).

**Testing:**
Tier1 in GHA: **OK** (Failures of `TestCPUAwareness.java` are [unrelated](https://github.com/openjdk/jdk8u-dev/pull/727))

-------------

Commit messages:
 - Backport 7b1455163ed893639059b3d62b71b2ff347c2e3f

Changes: https://git.openjdk.org/jdk8u-dev/pull/733/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=733&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8074840
  Stats: 54 lines in 12 files changed: 16 ins; 12 del; 26 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/733.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/733/head:pull/733

PR: https://git.openjdk.org/jdk8u-dev/pull/733