libmvec on aarch64 without hardware SVE support

[Andreas K. Huettel]

> Hi Andreas,
> 
> > > configure:331: aarch64-unknown-linux-gnu-gcc  -mcpu=native -pipe -O2 -Wl,-O1 -Wl,--as-needed -c -march=armv8.2-a+sve conftest.s 1>&5
> 
> I believe you can only get that if you accidentally add -mcpu=native to CC
> rather than to CFLAGS.
> 
> > I don't know how typical -mcpu=... usage in comparison to -march=... is, 
> > the failure I got with the CFLAGS forcing sve off probably falls under 
> > "self-inflicted pain" then. If the intention of the -march=armv8.2-a+sve 
> > in the configure test is to override user settings, it should fully do it
> > though.
> 
> We don't add CFLAGS here, so this works fine. If we used CFLAGS then
> these tests would have to use -mcpu since that takes precedence over
> -march.

Hi Wilco, 

Oh. Right. Thank you! Then it's indeed even more harmless since it is
(if at all) a Gentoo-only problem.

(Following advice from here long ago, we add for glibc the base CFLAGS 
to CC. I'd have to look up the rationale again myself; in general this
works very well though.)

So let's close this thread. Nothing to see here, nothing to do here, 
just move along please.

Best,
Andreas

--
Andreas K. Hüttel
dilfridge@gentoo.org
Gentoo Linux developer
(council, toolchain, base-system, perl, libreoffice)
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