add arm-features.h from glibc source

[sv99]

Problems with -target arm-linux-gnueabi

zig build-exe hello.c -target arm-linux-gnueabi --library c --verbose-cc --name hello-zig

...
In file included from /usr/local/Cellar/zig/0.9.1_1/lib/zig/libc/glibc/sysdeps/unix/sysv/linux/arm/sysdep.h:25:
In file included from /usr/local/Cellar/zig/0.9.1_1/lib/zig/libc/glibc/sysdeps/unix/arm/sysdep.h:19:
/usr/local/Cellar/zig/0.9.1_1/lib/zig/libc/glibc/sysdeps/arm/sysdep.h:25:11: fatal error: 'arm-features.h' file not found
...

Add file arm-features.h from the glibc source.

[sv99]

May be close #3287

[matu3ba]

missing 1. test coverage (see test/standalone), 2. CI qemu fixup, and (but very unsure) 3. brief clarification/ensuring that this does not mess up the glibc update routine.

[sv99]

This is simple header file - what need test?

fatal error: 'arm-features.h' file not found
# include <arm-features.h>

Workaround - manually add this header file. After this - build success.

[matu3ba]

what need test

arm gnu crosscompiling + running needs tests in CI. Sorry, I have not been explicit from the beginning. See #3174

[billzez]

I can verify that this works and builds working executables. Going back through older releases of zig, I could not find a version that includes a glibc that can build 32-bit arm binaries.

[jedisct1]

Thank you!

Not sure why that file had been forgotten, but its addition indeed allows zig cc to finally support that target.

Thanks!

[matu3ba]

@jedisct1

This is missing CI coverage:

"Is there more to this than just merging #12346?"
"Perhaps not, but it is my duty to test & verify patches from first-time contributors. I also need to run the test suite for armv8-linux-gnueabihf and find out if the tests then pass and if so, enable more CI test coverage."

[jedisct1]

arm-linux is still Tier 2 "These targets are known to work, but may not be automatically tested".