[RFR] 8217753: Enable HotSpot builds on 5.x Linux kernels

[Andrew John Hughes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8217753
Webrev: https://cr.openjdk.java.net/~andrew/openjdk8/8217753/webrev.01/

This is 8u and below only as it's part of the old HotSpot build replaced
in 9+.

There's a check in make/linux/Makefile to ensure that a 2.4 or later
kernel is being used. This has been extended by JDK-7072341 to
accommodate Linux 3.x and JDK-8074312 for 4.x. 5.x is now imminent [0]
and the build is broken again [1].

Given that 2.4 was released over 18 years ago [2], I think now is the
time to just get rid of this check rather than bumping it yet again. If
anyone is really trying to build OpenJDK 8 on a 2.2 kernel, I suspect
they will encounter other issues than a Makefile check, and it seems far
more likely that, if we just add a '5%' check, someone is going to build
with Linux 6.x in a few years and hit this same bug again.

[0] https://lwn.net/Articles/776034/
[1] https://bugs.gentoo.org/675920
[2] http://lkml.iu.edu/hypermail/linux/kernel/0101.0/0776.html
-- 
Andrew :)

Senior Free Java Software Engineer
Red Hat, Inc. (http://www.redhat.com)

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