[docs] Change the output path on macOS

[email protected]

Change-Id: I7a4c65e651b88f7882eba9512adbe4e14b3fdefd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442900
Reviewed-by: Alexander Thomas <[email protected]>
Commit-Queue: Michael Goderbauer <[email protected]>
Reviewed-by: Michael Goderbauer <[email protected]>
Auto-Submit: Leonardo YongUk Kim <[email protected]>

Author: dalinaum

docs/Building.md

@@ -107,7 +107,7 @@ cd sdk
 ./tools/build.py --mode release create_sdk
 ```
 
-The output will be in `out/ReleaseX64/dart-sdk` on Linux and Windows, and `xcodebuild/ReleaseX64/dart-sdk` on macOS.
+The output will be in `out/ReleaseX64/dart-sdk` on Linux and Windows, and `xcodebuild/ReleaseARM64/dart-sdk` on macOS.
 
 See also [Building Dart SDK for ARM or RISC-V](Building-Dart-SDK-for-ARM-or-RISC-V.md).