script/lib.sh: set GOARM=5 for armel, GOARM=6 for armhf

[AkihiroSuda]

https://github.com/golang/go/wiki/GoArm#supported-operating-systems

ARM on Linux. You must run an EABI kernel.
These are generally known as armel for softfloat (compatible with ARMv5)
or armhf for hardware floating point (ARMv6 and above).

Prior to this commit, the script was setting GOARM=6 for armel, GOARM=7 for armhf.

Fix #4033

[AkihiroSuda]

https://wiki.debian.org/ArmHardFloatPort

In practice armel will be used for older CPUs (armv4t, armv5, armv6), and armhf for newer CPUs (armv7+VFP).

Debian wiki conflicts with Golang wiki.
Not sure which one is correct.

[AkihiroSuda]

https://wiki.debian.org/RaspberryPi

Raspberry Pi OS builds a single image for all of the Raspberry families, so you will get an armhf 32-bit, hard floating-point system, but built for the ARMv6 ISA (with VFP2), unlike Debian's ARMv7 ISA (with VFP3) port.

Looks like armhf means ARMv7 for Debian, ARMv6 for Raspbian 🤯 .

So it looks like this PR still makes a sense for Raspbian users.

[kolyshkin]

Originally, these values for GOARM (6 and 7) come from PR #1820 (commit 39f679c).

My guess is https://wiki.debian.org/ArmHardFloatPort (last modified in 2017) is wrong/outdated to say armhf requires v7, since the other two sources say v6.

OTOH https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html says

Note that floating-point is not supported by the base ARMv7-M architecture, but is compatible with both the ARMv7-A and ARMv7-R architectures.

Meaning, even v7 can require soft-float, depending on the hardware. So, it's a maze.

[kolyshkin]

Also, since no one ever complained about how we build our binaries, maybe we are doing it right?

[tianon]

The Debian wiki isn't outdated; rather within Debian (read: Raspbian is not Debian), there is officially no v6 (hence the Raspbian rebuild), only v5 (armel) and v7 (armhf). It might be better to use less ambiguous names like armv5, armv6, armv7, but generally armv5 binaries will work fine on both v5 and v6 devices, so this change is sane IMO.

[tianon]

For (up to date) baselines within Debian, https://wiki.debian.org/ArchitectureSpecificsMemo#Architecture_baselines is probably a better reference.

[kolyshkin]

It might be better to use less ambiguous names like armv5, armv6, armv7

Yes, I think this is what we should do @AkihiroSuda, instead of using armel and armhf we should use armv5, armv6, armv7 (and choose hf for the last two).

[kolyshkin]

LGTM, but maybe we should change the naming as suggested by @tianon

[AkihiroSuda]

LGTM, but maybe we should change the naming as suggested by @tianon

Not in this PR, as it will break third-party installation scripts that curls runc

[thaJeztah]

LGTM