[build] Update Swift version in Info.plist for locally built toolchains

Currently for toolchains built locally via `build-toolchain`, the version in `Info.plist` is `5.0.YYYYMMDD`.
Since the main branch is currently targeting Swift 5.8, let's bump the version in `Info.plist`.

Author: egorzhdan

utils/build-toolchain

@@ -123,7 +123,7 @@ set -x
 YEAR=$(date +"%Y")
 MONTH=$(date +"%m")
 DAY=$(date +"%d")
-TOOLCHAIN_VERSION="5.0.${YEAR}${MONTH}${DAY}"
+TOOLCHAIN_VERSION="5.8.${YEAR}${MONTH}${DAY}"
 TOOLCHAIN_NAME="swift-LOCAL-${YEAR}-${MONTH}-${DAY}-a"
 DARWIN_TOOLCHAIN_VERSION="0.0.${YEAR}${MONTH}${DAY}"
 ARCHIVE="${TOOLCHAIN_NAME}-${OS_SUFFIX}.tar.gz"