Add empty ctrlc handler on Windows.

Cargo.toml

@@ -67,6 +67,7 @@ rustc-workspace-hack = "1.0.0"
 core-foundation = { version = "0.6.0", features = ["mac_os_10_7_support"] }
 
 [target.'cfg(windows)'.dependencies]
+ctrlc = "3.1.1"
 miow = "0.3.1"
 fwdansi = "1"
 

src/cargo/lib.rs

@@ -20,6 +20,8 @@ extern crate clap;
 extern crate core_foundation;
 extern crate crates_io as registry;
 extern crate crossbeam_utils;
+#[cfg(windows)]
+extern crate ctrlc;
 extern crate curl;
 #[macro_use]
 extern crate failure;

src/cargo/util/process_builder.rs

@@ -170,9 +170,11 @@ impl ProcessBuilder {
 
     /// On unix, executes the process using the unix syscall `execvp`, which will block this
     /// process, and will only return if there is an error. On windows this is a synonym for
-    /// `exec`.
+    /// `exec`, except we install a ctrlc handler first to prevent us from eating
+    /// the signal the subprocess may care about.
     #[cfg(windows)]
     pub fn exec_replace(&self) -> CargoResult<()> {
+        ::ctrlc::set_handler(move || {} )?;
         self.exec()
     }