fix(core): probe driver version lazily in Linker dispatch

driver_version() was called unconditionally during Linker.__init__,
which fails in environments where nvJitLink is installed but the
CUDA driver is absent (e.g., build containers). Now catches the
exception and sets driver_major=None. When driver_major is unknown
and nvJitLink is available, optimistically selects the nvJitLink
backend.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: cpcloud

cuda_core/cuda/core/_linker.pyx

@@ -472,7 +472,13 @@ cdef inline int Linker_init(Linker self, tuple object_codes, object options) exc
     )
     lto_requested = bool(options.link_time_optimization) or bool(options.ptx)
     nvjitlink_version = _probe_nvjitlink()
-    driver_major = driver_version()[0]
+    # Probe driver version lazily: only needed when comparing majors.
+    # In environments where nvJitLink is installed but the driver is
+    # absent (e.g., build containers), we can still select nvJitLink.
+    try:
+        driver_major = driver_version()[0]
+    except Exception:
+        driver_major = None
     backend = _choose_backend(
         driver_major, nvjitlink_version, inputs_have_ltoir, lto_requested
     )
@@ -701,7 +707,7 @@ def _probe_nvjitlink() -> tuple | None:
 
 
 def _choose_backend(
-    driver_major: int,
+    driver_major: int | None,
     nvjitlink_version: tuple | None,
     inputs_have_ltoir: bool,
     lto_requested: bool,
@@ -710,8 +716,9 @@ def _choose_backend(
 
     Parameters
     ----------
-    driver_major : int
+    driver_major : int or None
         Major version of the installed CUDA driver (from ``cuDriverGetVersion``).
+        ``None`` when the driver cannot be queried (e.g., no driver installed).
     nvjitlink_version : tuple[int, int] or None
         ``(major, minor)`` if nvJitLink is available and >=12.3; ``None`` otherwise.
     inputs_have_ltoir : bool
@@ -746,7 +753,9 @@ def _choose_backend(
         return "driver"
 
     nvjitlink_major = nvjitlink_version[0]
-    if nvjitlink_major == driver_major:
+    # If driver version is unknown, optimistically use nvJitLink
+    # (common in build containers with nvJitLink but no driver).
+    if driver_major is None or nvjitlink_major == driver_major:
         return "nvjitlink"
 
     if needs_nvjitlink: