Work around issue on toolchain with commit-date different than rustup…

… toolchain

Fixes #11

See #11 (comment) for more.

build.rs

@@ -162,7 +162,8 @@ mod version {
 
         pub(crate) fn probe(&self, minor: u32, year: u16, month: u8, day: u8) -> bool {
             if self.nightly {
-                self.minor > minor || self.commit_date >= Date::new(year, month, day)
+                self.minor > minor
+                    || self.minor == minor && self.commit_date >= Date::new(year, month, day)
             } else {
                 self.minor >= minor
             }