Cargo: Change lto option to "thin"

A recent version of nightly rust gets the following link error:

error: failed to get bitcode from object file for LTO (Bitcode section
not found in object file)

This issue can be fixed by supplying `-C linker-plugin-lto` and set lto
option to "thin"[1].

[1] hermit-os/hermit-rs#15

Signed-off-by: Akira Moroo <[email protected]>

Author: retrage

Cargo.toml

@@ -8,11 +8,11 @@ edition = "2018"
 # needed here to make "cargo check" and "cargo clippy" run without errors.
 [profile.dev]
 panic = "abort"
-lto = true
+lto = "thin"
 
 [profile.release]
 panic = "abort"
-lto = true
+lto = "thin"
 
 [features]
 default = ["log-serial", "log-panic"]