[librsvg] Cargo.toml: Turn on link-time optimizations in release mode

[Federico Mena Quintero <federico src gnome org>]

commit 39779313e9726af1ff6e806ae8df542906631b66
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri May 19 15:02:48 2017 -0500

    Cargo.toml: Turn on link-time optimizations in release mode
    
    Wow, this reduces the library size a lot!
    
    Thanks to Luke Nukem for the tip
    
    http://lukenukem.co.nz/gsoc/2017/05/16/gso_2.html

 rust/Cargo.toml |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index d5ee84c..a117a3d 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -55,3 +55,6 @@ version = "0.12.5"
 [lib]
 name = "rsvg_internals"
 crate-type = ["staticlib"]
+
+[profile.release]
+lto = true