fix(build.sh): clear ci directory without removing mount point

When ci/ is bind-mounted into cibuildwheel's container at /project/ci,
rm -rf ci fails with "Resource busy" because the mount point cannot be
removed from inside the container. Clear the directory contents instead,
and use mkdir -p so the command succeeds whether or not the directory
already exists.

Assisted-by: Kimi Code

Author: jdavid

build.sh

@@ -92,8 +92,10 @@ if [ "$CIBUILDWHEEL" = "1" ]; then
         exit 0
     fi
 
-    rm -rf ci
-    mkdir ci || true
+    # The ci directory may be a bind-mount (e.g. inside cibuildwheel), so
+    # remove its contents but keep the directory itself.
+    rm -rf ci/* ci/.[!.]* ci/..?* 2>/dev/null || true
+    mkdir -p ci
     cd ci
 else
     # Create a virtual environment