Harmonize CUDA support with NVCC default --cudart static.

This can interfere with current deployments in the wild, in which
case some adjustments might be required. Most notably one might
have to add .cuda("none") to the corresponding Builder instantiation
to restore the original behaviour.

Author: dot-asm

src/lib.rs

@@ -613,19 +613,21 @@ impl Build {
         self.cuda = cuda;
         if cuda {
             self.cpp = true;
+            self.cudart = Some("static".to_string());
         }
         self
     }
 
     /// Link CUDA run-time.
     ///
-    /// This option mimics the `--cudart` nvcc command-line option. Just like
-    /// the original it accepts `{none|shared|static}`. However, in case you
-    /// don't use this method when instantiating the `Build` class, the outcome
-    /// is equivalent to `none`. This is different from nvcc's default 'static'.
+    /// This option mimics the `--cudart` NVCC command-line option. Just like
+    /// the original it accepts `{none|shared|static}`, with default being
+    /// `static`. The method has to be invoked after `.cuda(true)`, or not
+    /// at all, if the default is right for the project.
     pub fn cudart(&mut self, cudart: &str) -> &mut Build {
-        self.cuda(true);
-        self.cudart = Some(cudart.to_string());
+        if self.cuda {
+            self.cudart = Some(cudart.to_string());
+        }
         self
     }