Runtime fixes/enhancements for static JDK work

[Jiangli Zhou]

Hello everyone,

I'd like to get input on some runtime fixes and enhancements [1] for
the static JDK support. The changes [1] include part of our hermetic
Java [2] prototype work towards more complete support for static JDK,
based on the existing JEP 178 [3] work. The changes mainly include the
following besides some miscellaneous small fixes:

1) Support unique names for
JNI_OnLoad|JNI_OnUnload|Agent_OnLoad|Agent_OnUnload|Agent_OnAttach in
JDK JNI libraries by default.

For both dynamic JDK and static JDK, this is to use unique symbols for
JNI_OnLoad function and friends. The
JNI_OnLoad|JNI_OnUnload|Agent_OnLoad|Agent_OnUnload|Agent_OnAttach
naming is handled by existing macros in
src/java.base/share/native/libjava/jni_util.h without additional
changes. Non-builtin application JNI libraries can still have the
default JNI_OnLoad|... naming.

We've found that it is useful for testing during the transition from
dynamic JDK to static JDK.

2) Use runtime checks to determine if the current execution is running
on static JDK or dynamic JDK. This allows the removal of the
STATIC_BUILD macro usages. With all STATIC_BUILD macro usages being
cleaned up, the same set of .o files produced by JDK build can be used
to create the shared libraries and static libraries (used for creating
the final static image). That seems to be a cleaner approach.

The changes [1] in the github branch currently have not cleaned up all
STATIC_BUILD macro usages yet. The number of usages [4] in (non-test)
JDK and hotspot is small (only in 11 files).

We've already recently integrated some of the static JDK related
changes, including duplicate symbol fixes and build changes for static
libraries. The main tracking bug is JDK-8303796 [5] currently. We'd
like your thoughts and opinions on if a new JEP would be needed/useful
for the additional runtime fixes/enhancement. The question has been
previously raised by Mark in JDK-8307858 [6] comments.

NOTES:
- For OS specific changes, the github branch currently only contains
changes for unix/linux port.
- I only ran HelloWorld using the bin/javastatic binary built from the
branch as a sanity test. I haven't run other tests with the changes on
top of the latest JDK head after porting (some of the porting included
some rework).

To build and try bin/javastatic on linux_x64:
$ bash configure --with-boot-jdk=<boot_jdk> --with-static-java=yes
$ make static-java-image

Best,
Jiangli

[1] https://github.com/openjdk/jdk/compare/master...jianglizhou:jdk:static-java
[2] https://mail.openjdk.org/pipermail/leyden-dev/2023-February/000107.html
[3] https://openjdk.org/jeps/178
[4] https://github.com/search?q=repo%3Aopenjdk%2Fjdk+STATIC_BUILD+NOT+path%3A%22test%2F%22+NOT+path%3A%22make%2F%22&type=code
[5] https://bugs.openjdk.org/browse/JDK-8303796
[6] https://bugs.openjdk.org/browse/JDK-8307858