From 5a55ed7cfb5c64cf61cea75ed80139217a8261c8 Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Thu, 9 Jul 2026 08:45:51 -0700
Subject: [PATCH] Nightly: fix Mac ARM64 build by targeting macOS 13.3 for
 std::format (#10075)

The Nightly **Mac ARM64 Build** job fails on current Xcode/libc++
because `std::format` pulls floating-point formatting paths that require
`std::to_chars` availability from macOS 13.3+. The job was still
compiling with a 13.0 deployment target.

- **Root cause**
  - ARM64 nightly job used:
    - `MACOSX_DEPLOYMENT_TARGET=13.0`
    - `mk_unix_dist.py --os=osx-13.0`
- This mismatched the effective libc++ requirements in the runner
toolchain.

- **Workflow change**
  - Updated only `.github/workflows/nightly.yml` for `mac-build-arm64`:
    - `MACOSX_DEPLOYMENT_TARGET: "13.0" -> "13.3"`
    - `--os=osx-13.0 -> --os=osx-13.3`

- **Resulting behavior**
- ARM64 nightly build target now aligns with the minimum OS level
required by the formatting code paths used by current compilation units.

```yaml
# .github/workflows/nightly.yml (mac-build-arm64)
env:
  MACOSX_DEPLOYMENT_TARGET: "13.3"

- name: Build
  run: python scripts/mk_unix_dist.py --dotnet-key=$GITHUB_WORKSPACE/resources/z3.snk --arch=arm64 --os=osx-13.3
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
---
 .github/workflows/nightly.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index df36d1f73d..d42aa02c9d 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -72,7 +72,7 @@ jobs:
     runs-on: macos-latest
     timeout-minutes: 90
     env:
-      MACOSX_DEPLOYMENT_TARGET: "13.0"
+      MACOSX_DEPLOYMENT_TARGET: "13.3"
     steps:
       - name: Checkout code
         uses: actions/checkout@v7.0.0
@@ -83,7 +83,7 @@ jobs:
           python-version: '3.x'
       
       - name: Build
-        run: python scripts/mk_unix_dist.py --dotnet-key=$GITHUB_WORKSPACE/resources/z3.snk --arch=arm64 --os=osx-13.0
+        run: python scripts/mk_unix_dist.py --dotnet-key=$GITHUB_WORKSPACE/resources/z3.snk --arch=arm64 --os=osx-13.3
             
       - name: Validate libz3.dylib and z3 architecture (must be arm64)
         run: |