RFR: 8255128: linux x86 build failure with libJNIPoint.c [v2]

[Jorn Vernee]

On Tue, 3 Nov 2020 19:08:05 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> I knew this looks familiar. Look at [existing macros in jlong_md.h](https://github.com/openjdk/jdk/blob/master/src/java.base/unix/native/libjava/jlong_md.h#L67-L81) and use/match them? There is a little difference in casting through `jint` in your code, while `jlong_md.h` does it via `int`.
>
> @shipilev Now that I look at the file you linked, it does look familiar to me as well. Must have copy-pasted it from my subconscious ;)
> 
> Looks like this file is usable from the benchmark lib code as well, will try to switch.

I've updated the PR with the following 2 changes:
- Use the pre-exsiting macros from jlong.h to convert between jlong and pointer
- Collapse the 2 if-blocks in flags-cflags.m4 for setting _LP64 into one

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PR: https://git.openjdk.java.net/jdk/pull/1017