Automatic reply from Jenkins: Can I test this?

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
gligar03.gligar.os - Linux SL 6.7, Intel(R) Xeon(R) CPU E5-2670 0 @ 2.60GHz, Python 2.6.6
See https://gist.github.com/6c16a2116650b4326c56 for a full test report.

Test report by @boegel
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
node2636.swalot.os - Linux centos linux 7.2.1511, Intel(R) Xeon(R) CPU E5-2660 v3 @ 2.60GHz, Python 2.7.5
See https://gist.github.com/5f90390b6ff39297272b for a full test report.

Jenkins: ok to test

Easyconfigs unit test suite PASSed (see https://jenkins1.ugent.be/job/easybuild-easyconfigs-pr-builder/7224/console for more details).

This pull request is now ready for review/testing.

Please try and find someone who can tackle this; contact @boegel if you're not sure what to do.

This looks OK, and it doesn't seem to break anything, but it would be nice to at least figure out why this works (so we can add a comment in the easyconfig to explain why it's required).

@wpoely86 Can you take a quick look?

It's a bit weird that this still is needed but looks harmless to me.

@wpoely86 It fixes the build on CentOS5, see also https://bugs.gentoo.org/show_bug.cgi?id=289757

The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline" functions
when in C99 mode.
This option is accepted and ignored by GCC versions 4.1.3 up to but not including 4.3.
In GCC versions 4.3 and later it changes the behavior of GCC in C99 mode.
Using this option is roughly equivalent to adding the "gnu_inline" function attribute to all inline functions.

This doesn't help me a lot in explaining why it fixes the problem, but it does suggest it's harmless to include it.

I'll merge this and #2779 after testing, and then apply this change to all the M4 easyconfigs...

Going in, thanks @SimonPinches!

PR to sync up all M4 1.4.17 easyconfigs is at #2816