Use empty blas_ldflags if no cxx is configured

pytensor/link/c/cmodule.py

@@ -2773,6 +2773,9 @@ def default_blas_ldflags():
         else:
             raise RuntimeError(f"Supplied flags {flags} failed to compile")
 
+    # If no compiler is available we default to empty ldflags
+    if not config.cxx:
+        return ""
     _std_lib_dirs = std_lib_dirs()
     if len(_std_lib_dirs) > 0:
         rpath = _std_lib_dirs[0]

tests/link/c/test_cmodule.py

@@ -226,6 +226,11 @@ def test_default_blas_ldflags(
             )
 
 
+def test_default_blas_ldflags_no_cxx():
+    with pytensor.config.change_flags(cxx=""):
+        assert default_blas_ldflags() == ""
+
+
 @patch(
     "os.listdir", return_value=["mkl_core.1.dll", "mkl_rt.1.0.dll", "mkl_rt.1.1.lib"]
 )