Update LLVM to get slightly better memcpy elision

diff --git a/src/llvm b/src/llvm
index c9b823739d1357a058e7437c00bec6d2d0b00ed6..ec1fdb3b9d3b1fb9e1dae97a65dd3a13db9bfb23 160000 (submodule)
--- a/src/llvm
+++ b/src/llvm
@@ -1 +1 @@
-Subproject commit c9b823739d1357a058e7437c00bec6d2d0b00ed6
+Subproject commit ec1fdb3b9d3b1fb9e1dae97a65dd3a13db9bfb23