There's a bug preventing us from booting TockOS in debug builds, so turn off all optimizations for TockOS app and increase stack size so it still runs.

Change-Id: I5890ace6ce5f44d10e61fdc35bd6dcb887979906

Cargo.toml

diff --git a/Cargo.toml b/Cargo.toml
index 70200fd..ac8f6df 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -75,6 +75,7 @@
 panic = "abort"
 lto = true
 debug = true
+opt-level = 0
 
 [profile.release]
 panic = "abort"

examples/hello_world.rs

diff --git a/examples/hello_world.rs b/examples/hello_world.rs
index 2872f25..796007a 100644
--- a/examples/hello_world.rs
+++ b/examples/hello_world.rs
@@ -7,7 +7,8 @@
 use libtock::println;
 use libtock::result::TockResult;
 
-libtock_core::stack_size! {0x400}
+// Must be at least 4k in debug builds.
+libtock_core::stack_size! {0x1000}
 
 #[libtock::main]
 async fn main() -> TockResult<()> {