INTPYTHON-757 Force usage of cmake 3 on MacOS GHA runners (#350)

Author: blink1073

.github/workflows/dist-python.yml

@@ -80,6 +80,12 @@ jobs:
         if: runner.os == 'macOS'
         run: brew install pkg-config
 
+      - name: Install CMake 3 on MacOS
+        # libbson requires cmake 3, and cmake 4 is now the default on the GHA runners.
+        if: ${{ startsWith(runner.os, 'macOS') }}
+        run: |
+          pipx install "cmake>=3.15,<4"
+
       - name: Install deps
         run: python -m pip install "cibuildwheel>=2.4,<3" uv rust-just
 
@@ -108,7 +114,7 @@ jobs:
 
   make_sdist:
     name: Make SDist
-    runs-on: macos-latest
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
         with:

.github/workflows/test-python.yml

@@ -60,6 +60,11 @@ jobs:
         with:
           mongodb-version: 4.4
           mongodb-replica-set: test-rs
+      - name: Install CMake 3 on MacOS
+        # libbson requires cmake 3, and cmake 4 is now the default on the GHA runners.
+        if: ${{ startsWith(runner.os, 'macOS') }}
+        run: |
+          pipx install "cmake>=3.15,<4"
       - name: Start MongoDB on MacOS
         if: ${{ startsWith(runner.os, 'macOS') }}
         run: |