Try to fix build-std

Author: Gelbpunkt

.cargo/config.toml

@@ -1,5 +1,5 @@
 [unstable]
-build-std = ["std", "panic_abort"]
+build-std = ["core", "alloc", "std", "panic_abort"]
 build-std-features = ["panic_immediate_abort"]
 
 [target.x86_64-unknown-linux-gnu]