examples: Pin proc-macro2 dependency

See <Rahix/avr-hal#537> for details.

Author: Rahix

examples/atmega328p/Cargo.toml

@@ -24,6 +24,12 @@ version = "0.5.3"
 # path = "../.."
 features = ["atmega328p", "rt"]
 
+# The latest releases of `proc-macro2` do not support the rust toolchain that
+# we use.  Thus, we must fix this dependency to an older version where our
+# toolchain is still supported.  See https://github.com/Rahix/avr-hal/issues/537
+[build-dependencies.proc-macro2]
+version = "=1.0.79"
+
 # Configure the build for minimal size - AVRs have very little program memory
 [profile.dev]
 panic = "abort"