examples: Fix build-std settings for compiler-builtins

This is a workaround to ensure intrinsics get linked in from avr-libc
instead of Rust's compiler-builtins.  The problem is that the versions
from compiler-builtins have slightly different calling convention and as
such cannot actually be substituted for the versions from avr-libc right
now.

This should fix a lot of the observed problems with 32-bit arithmetic.

Ref: rust-lang/rust#82242 (comment)

examples/arduino-diecimila/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude diecimila"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/arduino-leonardo/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude leonardo"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/arduino-mega2560/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude -cb 57600 mega2560"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/arduino-nano/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude nano -cb 57600"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/arduino-uno/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude uno -cb 57600"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/nano168/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude nano168 -cb 57600"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/sparkfun-promicro/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude promicro"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/trinket-pro/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude trinket-pro"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]

examples/trinket/.cargo/config.toml

@@ -6,3 +6,4 @@ runner = "ravedude trinket"
 
 [unstable]
 build-std = ["core"]
+build-std-features = ["compiler-builtins-mangled-names"]