Update Illumos sysroot

[nikic]

@jclulow @pfmooney

The Illumos sysroot used by the dist-x86_64-illumos build is very outdated, dating back to 2018:

rust/src/ci/docker/scripts/illumos-toolchain.sh

Lines 50 to 55 in d9617c8

	SYSROOT_VER='20181213-de6af22ae73b-v1'
	SYSROOT_SUM='ee792d956dfa6967453cebe9286a149143290d296a8ce4b8a91d36bea89f8112'
	SYSROOT_TAR="illumos-sysroot-$SYSROOT_MACH-$SYSROOT_VER.tar.gz"
	SYSROOT_URL='https://github.com/illumos/sysroot/releases/download/'
	SYSROOT_URL+="$SYSROOT_VER/$SYSROOT_TAR"
	SYSROOT_DIR="$PREFIX/sysroot"

This needs to be updated to a newer version which at least includes the fix for https://www.illumos.org/issues/14418. LLVM 22 fails to build against the outdated Illumos sysroot, and given that the issue has been fixed upstream, I don't think we should work around this bug as we did in the past.

I don't see any newer sysroot releases on https://github.com/illumos/sysroot/releases, so I don't know how to do this myself. Are the sysroots published in some different place now?

[pfmooney]

Yes, sorry. This has been something we (I) have been meaning to get to, and have dropped the ball on.

[pfmooney]

I've raised it for discussion in the project. Hopefully it reaches quick consensus, and we'll create a much more recent sysroot for use here.

[nikic]

Thanks! I'm not familiar with how decision making in IllumOS works, I assume it's going to take a while for this to be accepted?

In the meantime, I'll add this patch to our LLVM fork to work around the specific issue I ran into:

From 45f9c6b4ee8914e90c933b692923da5d0fff3d64 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Fri, 23 Jan 2026 10:56:56 +0100
Subject: [PATCH] [rust] Work around illumos build failure

---
 lld/MachO/Driver.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
index 973b3f5535cb..7a27a9986bc8 100644
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -372,7 +372,11 @@ void multiThreadedPageInBackground(DeferredFiles &deferred) {
 #define DEBUG_TYPE "lld-madvise"
     auto aligned =
         llvm::alignDown(reinterpret_cast<uintptr_t>(buff.data()), pageSize);
+#if defined(POSIX_MADV_WILLNEED)
+    if (posix_madvise((void *)aligned, buff.size(), POSIX_MADV_WILLNEED) < 0)
+#else
     if (madvise((void *)aligned, buff.size(), MADV_WILLNEED) < 0)
+#endif
       LLVM_DEBUG(llvm::dbgs() << "madvise error: " << strerror(errno) << "\n");
 #undef DEBUG_TYPE
 #endif
-- 
2.52.0