RFR: 8304674: File java.c compile error with -fsanitize=address -O0 [v3]

[SendaoYan]

> Hi all,
> File src/java.base/share/native/libjli/java.c compile error: control reaches end of non-void function [-Werror=return-type] with gcc options -fsanitize=address -O0. The function int JavaMain(void* _args) in this file will execute return ret in LEAVE() macro, but gcc with -O0 is not smart enough to recognized that the function already has return statement before at the end of function. It's a gcc bug which has been recorded by [80959](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80959), and below code snippet can demonstrate the gcc bug. I think we should disable return-type gcc warning for java.c file before the gcc bug has been fixed. Risk is low.
> 
> 
>> cat java.c
> char a() {
>   return 0;
>   int b;
>   if (a(&b))
>     return 0;
> }
> 
>> gcc -O0 -Wall -Wextra -Werror -O0 -c java.c -fsanitize=address
> java.c: In function ‘a’:
> java.c:6:1: error: control reaches end of non-void function [-Werror=return-type]
>     6 | }
>       | ^
> cc1: all warnings being treated as errors

SendaoYan has updated the pull request incrementally with one additional commit since the last revision:

  add "#if defined(__GNUC__)" to fix windows build warning

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24318/files
  - new: https://git.openjdk.org/jdk/pull/24318/files/83beb975..8d929c8d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24318&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24318&range=01-02

  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24318.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24318/head:pull/24318

PR: https://git.openjdk.org/jdk/pull/24318