Add firmware-devel profile to cargo config

This speeds up compile time in exchange for binary size,
which is often a worthy trade-off in development when iteration speed
matters.

.cargo/config.toml

@@ -36,6 +36,11 @@ lto = "fat"
 opt-level = "z"
 strip = "debuginfo"
 
+[profile.firmware-devel]
+inherits = "release"
+opt-level = "s"
+lto = false
+
 # optimizations to reduce the binary size of firmware binaries
 [profile.firmware]
 inherits = "release"