Lower requirement for prebuilt binary, arm64

[jpike88]

Amazon Linux 2 for ARM (graviton) has a glibc version of 2.26.

Prebuilt binary requires 2.29.

Can this requirement be lowered to 2.26?

[lovell]

Hi, please see lovell/sharp-libvips@2e4202d and lovell/sharp-libvips#86 for previous discussion and attempts to use an earlier glibc.

The summary is that a minimum of gcc 9.1.0+ is required to cross-compile libvips for ARM64, and gcc 9.1.0+ is only available on Debian-based OS with glibc 2.29+. (Other Linux flavours such as RHEL do not provide the cross-compilation toolchains we need.)

If anyone can solve this then a PR will be gladly accepted, but I'm going to close this request as it's probably a significant amount of work.

[lovell]

Possible future experiment that might help - see lovell/sharp-libvips#114

[lovell]

Tracking this at #2938