RFR: 8346433: Cannot use DllMain in hotspot for static builds [v3]

[Magnus Ihse Bursie]

> To be able to properly support static builds on Windows in [JDK-8346377](https://bugs.openjdk.org/browse/JDK-8346377), we cannot use DllMain, for two reasons:
> 
> 1) This is not called for statically linked libraries, and
> 2) There are multiple DllMain definitions throughout the JDK native libraries, causing name collisions.
> 
> While it could have been possible to keep the DllMain function for non-static builds and just use an alternative solution for static builds, I think it is preferable to have a single solution that works as well for both static and dynamic builds.
> 
> The DllMain in hotspot is doing work both at DLL load time, and at DLL unload time. Let's go through them to see why this patch is safe.
> 
> During DLL load time, the library handle is set, and the hi-res timer is initialized. The `pre_initialize` method from `WindowsDbgHelp` and `SymbolEngine` is called. These two are basically identical; both setup a critical section (a Windows mutex). However, this mutex is only used from a stack local guard object, which is allocated only when calls are made into these classes, which are not happening at bootstrapping time, so this shift in initialization time is harmless.
> 
> That shift in time is also very small. The `DllMain` method is called by Windows when the DLL is loaded (by libjli), and the very first thing that JLI does after that is to call `JNI_CreateJavaVM`, which ends up calling  `Threads::create_vm`, which calls `os::init` early on.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Update comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22793/files
  - new: https://git.openjdk.org/jdk/pull/22793/files/b658c560..98777912

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22793&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22793&range=01-02

  Stats: 4 lines in 4 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22793.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22793/head:pull/22793

PR: https://git.openjdk.org/jdk/pull/22793