RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v5]

[Magnus Ihse Bursie]

On Fri, 1 Dec 2023 10:02:35 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Did you try to find the libsleef by passing `--with-libsleef=` ? Currently `--with-libsleef=` can only work for people manually built from sleef source code.
>
> Yes. It still failed.

You need to expand this logic to cover more instances. See e.g. lib-ffi.m4 for inspiration.

Basic flow:
* if user has specified libsleef root with argument, check both lib/ and lib64/ under that root.
* if user has not specified libsleef root, and we have no SYSROOT, try PKG_CHECK
* Otherwise, look in well-known directories which is $SYSROOT/usr/[local/]lib[64].

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PR Review Comment: https://git.openjdk.org/jdk/pull/16234#discussion_r1412340745