Linux 6.19: handle --werror with CONFIG_OBJTOOL_WERROR=y

[john-cabaj]

Motivation and Context

When building against a 6.19 kernel using the Ubuntu 26.04 development build with CONFIG_OBJTOOL_WERROR=y, the zfs-linux DKMS package fails to build due to the following errors:

LD [M]  spl.o
spl.o: error: objtool: spl_kmem_cache_destroy+0x23d: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: spl_kmem_cache_create+0x5f4: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: kstat_seq_data_addr+0x77: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: __kstat_delete+0x7b: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: kstat_seq_show+0x137: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: __kstat_create+0x2b0: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: kstat_seq_start+0x365: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: taskq_destroy+0x32f: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns.h
spl.o: error: objtool: taskq_create_synced+0xcb: spl_panic() missing __noreturn in .c/.h or NORETURN() in noreturns

This is because the upstream Linux kernel introduced a change in 6.19-rc1 (56754f0f46f6: "objtool: Rename --Werror to --werror"), which doesn't match the changes in scripts/objtool-wrapper.in to ignore the compiler flag.

Description

Simple change to modify scripts/objtool-wrapper.in to look for both "--Werror" and "--werror", rather than just the former.

How Has This Been Tested?

This was tested in a QEMU environment using virtme-ng, after bisecting the Linux kernel changes down to the aforementioned commit. Using the changes in this PR, zfs-linux successfully built.

Tests were repeated on a LXD VM, whereupon some simple regression tests were also executed, notably the tests from here - https://git.launchpad.net/~canonical-kernel-team/+git/autotest-client-tests (see "ubuntu_zfs_*" tests).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Quality assurance (non-breaking change which makes the code more robust against bugs)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[john-cabaj]

Modifying the commit message and PR title to indicate this is needed for Linux 6.19 compat. No functional changes.