llvm: bump past v0.8.26 for the macOS nodeps dylib fix and drop the macOS linkstatic defaults (follow-up to #8114) #9228

Follow-up to #8114. hermeticbuild/hermetic-llvm#906 (merged 2026-11-02) drops supports_dynamic_linker on macOS, so cc_library builds no nodeps dylibs. Latest release v0.8.26 (2026-10-26) does not contain it. Until it ships, rules_dx's cc_test and cc_library macros default linkstatic = True on macOS.

Blocked on: a hermetic-llvm release after v0.8.26 containing hermeticbuild/hermetic-llvm#906 (https://github.com/hermeticbuild/hermetic-llvm/releases)

Where

• MODULE.bazel:71-80: llvm 0.8.26 pin and single_version_override.
• families/*/third_party/rules_dx/rules_dx.MODULE.bazel: vendored llvm pins.
• cc/rules/defs.bzl: the @platforms//os:macos branch of the linkstatic select in cc_test and cc_library.
• cc/rules/wrapper_tests.bzl, cc/tests/fixtures/hello/BUILD.bazel: the macOS static-link analysis tests.

Fix

• Bump llvm to the first release containing #772: Atomic dx update with rollback plan #906 everywhere it is pinned. Rebase the existing llvm patches.
• Remove the macOS branch from both linkstatic selects. Keep Windows as it is. Keep the analysis tests: they should still pass because the toolchain now builds no dylibs.
• Verify with evidence.yml, scope //tools/testing/hermetic:cpp_rust //cc/..., platforms ["macos_arm64"].