RFR: 8257913: Add more known library locations to simplify Linux cross-compilation [v3]

[Aleksey Shipilev]

On Mon, 8 Mar 2021 23:29:25 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> I thought we need to declare these as `AC_SUBST` as we define the variables outside this file? I can revert these additions if you think these are incorrect.
>
> No, they are only needed to be able to populate the @FOO@ tags in spec.gmk.in. All the *.m4 files are concatenated into a single shell script by autoconf, so referring to variables in a different m4 file does not really matter.
> 
> I don't think it's worth a separate bug to remove them, but if you touch the area again you can get rid of them while you're at it :)

Noted. Thanks!

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PR: https://git.openjdk.java.net/jdk/pull/2833