chore: update the target compiler version to nightly-2020-12-15

yvt · yvt · commit 0ea67670ca6e · 2020-12-17T00:00:18.000+09:00
diff --git a/rust-toolchain b/rust-toolchain
@@ -1 +1 @@
-nightly-2020-11-25
+nightly-2020-12-15
