Add support for Apple Silicon

Author: msanders

.swift-version

@@ -1 +1 @@
-5.1
+5.3

.travis.yml

@@ -3,7 +3,7 @@ addons:
     update: true
 language: swift
 os: osx
-osx_image: xcode11.3
+osx_image: xcode12.2
 before_install:
   - cd "$(mktemp -d)"
   - echo "859c18f80d547d0911fafe1a83696a19dfc6bfdeea69129c0097fd34cfe56ceb  ./shellcheck.rb" >> formulas.sha256sum

Makefile

@@ -1,6 +1,6 @@
 .PHONY: build
 build: ## Build debug target for development.
-	swift build
+	swift build --arch arm64 --arch x86_64
 
 .PHONY: help
 help: ## Print help information.

script/archive

@@ -11,10 +11,11 @@ build_release_target() {
 
     # Sandbox must be disabled for Homebrew builds. See
     # https://github.com/yonaskolb/XcodeGen/issues/51#issuecomment-331615462
-    swift build -c release -Xswiftc -Osize ${DISABLE_SANDBOX:+--disable-sandbox}
+    swift build --configuration release --arch arm64 --arch x86_64 \
+        -Xswiftc -Osize ${DISABLE_SANDBOX:+--disable-sandbox}
 
     mkdir -p "$ARCHIVE_DIR"
-    cp .build/release/zero "$ARCHIVE_DIR"
+    cp .build/apple/Products/Release/zero "$ARCHIVE_DIR"
     strip "$ARCHIVE_DIR/zero"
     set +x