Fallback to x86-64 release when macOS ARM 64-bit build not available

Apple's Rosetta 2 software allows applications built for x86-64 hosts to run on machines using their ARM 64-bit M1
processor.

Due to current infrastructure challenges (e.g., lack of GitHub-hosted GitHub Actions runners), Arduino Lint is not yet
available as a native M1 build, yet the existing macOS x86-64 builds work perfectly well on these machines thanks to
Rosetta 2.

The installation script previously failed to install Arduino Lint when ran on the M1 host:

Did not find a release for your system: macOS arm64

Author: per1234

etc/install.sh

@@ -40,6 +40,7 @@ initArch() {
   armv6*) ARCH="ARMv6" ;;
   armv7*) ARCH="ARMv7" ;;
   aarch64) ARCH="ARM64" ;;
+  arm64) ARCH="ARM64" ;;
   x86) ARCH="32bit" ;;
   x86_64) ARCH="64bit" ;;
   i686) ARCH="32bit" ;;
@@ -48,6 +49,15 @@ initArch() {
   echo "ARCH=$ARCH"
 }
 
+initFallbackArch() {
+  case "${OS}_${ARCH}" in
+  macOS_ARM64)
+    # Rosetta 2 allows applications built for x86-64 hosts to run on the ARM 64-bit M1 processor
+    FALLBACK_ARCH='64bit'
+    ;;
+  esac
+}
+
 initOS() {
   OS=$(uname -s)
   case "$OS" in
@@ -106,52 +116,69 @@ downloadFile() {
     TAG=$1
   fi
   #  arduino-lint_0.4.0-rc1_Linux_64bit.[tar.gz, zip]
+  APPLICATION_DIST_PREFIX="${PROJECT_NAME}_${TAG}_"
   if [ "$OS" = "Windows" ]; then
-    APPLICATION_DIST="${PROJECT_NAME}_${TAG}_${OS}_${ARCH}.zip"
+    APPLICATION_DIST_EXTENSION=".zip"
   else
-    APPLICATION_DIST="${PROJECT_NAME}_${TAG}_${OS}_${ARCH}.tar.gz"
+    APPLICATION_DIST_EXTENSION=".tar.gz"
   fi
+  APPLICATION_DIST="${APPLICATION_DIST_PREFIX}${OS}_${ARCH}${APPLICATION_DIST_EXTENSION}"
 
   # Support specifying nightly build versions (e.g., "nightly-latest") via the script argument.
   case "$TAG" in
   nightly*)
-    DOWNLOAD_URL="https://downloads.arduino.cc/${PROJECT_NAME}/nightly/${APPLICATION_DIST}"
+    DOWNLOAD_URL_PREFIX="https://downloads.arduino.cc/${PROJECT_NAME}/nightly/"
     ;;
   *)
-    DOWNLOAD_URL="https://downloads.arduino.cc/${PROJECT_NAME}/${APPLICATION_DIST}"
+    DOWNLOAD_URL_PREFIX="https://downloads.arduino.cc/${PROJECT_NAME}/"
     ;;
   esac
+  DOWNLOAD_URL="${DOWNLOAD_URL_PREFIX}${APPLICATION_DIST}"
 
   INSTALLATION_TMP_FILE="/tmp/$APPLICATION_DIST"
   echo "Downloading $DOWNLOAD_URL"
   httpStatusCode=$(getFile "$DOWNLOAD_URL" "$INSTALLATION_TMP_FILE")
   if [ "$httpStatusCode" -ne 200 ]; then
-    echo "Did not find a release for your system: $OS $ARCH"
-    echo "Trying to find a release using the GitHub API."
-
-    LATEST_RELEASE_URL="https://api.github.com/repos/${PROJECT_OWNER}/$PROJECT_NAME/releases/tags/$TAG"
-    if [ "$DOWNLOAD_TOOL" = "curl" ]; then
-      HTTP_RESPONSE=$(curl -sL --write-out 'HTTPSTATUS:%{http_code}' "$LATEST_RELEASE_URL")
-      HTTP_STATUS_CODE=$(echo "$HTTP_RESPONSE" | tr -d '\n' | sed -e 's/.*HTTPSTATUS://')
-      BODY=$(echo "$HTTP_RESPONSE" | sed -e 's/HTTPSTATUS\:.*//g')
-    elif [ "$DOWNLOAD_TOOL" = "wget" ]; then
-      TMP_FILE=$(mktemp)
-      BODY=$(wget --server-response --content-on-error -q -O - "$LATEST_RELEASE_URL" 2>"$TMP_FILE" || true)
-      HTTP_STATUS_CODE=$(awk '/^  HTTP/{print $2}' "$TMP_FILE")
-    fi
-    if [ "$HTTP_STATUS_CODE" != 200 ]; then
-      echo "Request failed with HTTP status code $HTTP_STATUS_CODE"
-      fail "Body: $BODY"
+    if [ -n "$FALLBACK_ARCH" ]; then
+      echo "$OS $ARCH release not currently available. Checking for alternative $OS $FALLBACK_ARCH release for your system."
+      FALLBACK_APPLICATION_DIST="${APPLICATION_DIST_PREFIX}${OS}_${FALLBACK_ARCH}${APPLICATION_DIST_EXTENSION}"
+      DOWNLOAD_URL="${DOWNLOAD_URL_PREFIX}${FALLBACK_APPLICATION_DIST}"
+      echo "Downloading $DOWNLOAD_URL"
+      httpStatusCode=$(getFile "$DOWNLOAD_URL" "$INSTALLATION_TMP_FILE")
     fi
 
-    # || true forces this command to not catch error if grep does not find anything
-    DOWNLOAD_URL=$(echo "$BODY" | grep 'browser_' | cut -d\" -f4 | grep "$APPLICATION_DIST") || true
-    if [ -z "$DOWNLOAD_URL" ]; then
-      echo "Sorry, we dont have a dist for your system: $OS $ARCH"
-      fail "You can request one here: https://github.com/${PROJECT_OWNER}/$PROJECT_NAME/issues"
-    else
-      echo "Downloading $DOWNLOAD_URL"
-      getFile "$DOWNLOAD_URL" "$INSTALLATION_TMP_FILE"
+    if [ "$httpStatusCode" -ne 200 ]; then
+      echo "Did not find a release for your system: $OS $ARCH"
+      echo "Trying to find a release using the GitHub API."
+
+      LATEST_RELEASE_URL="https://api.github.com/repos/${PROJECT_OWNER}/$PROJECT_NAME/releases/tags/$TAG"
+      if [ "$DOWNLOAD_TOOL" = "curl" ]; then
+        HTTP_RESPONSE=$(curl -sL --write-out 'HTTPSTATUS:%{http_code}' "$LATEST_RELEASE_URL")
+        HTTP_STATUS_CODE=$(echo "$HTTP_RESPONSE" | tr -d '\n' | sed -e 's/.*HTTPSTATUS://')
+        BODY=$(echo "$HTTP_RESPONSE" | sed -e 's/HTTPSTATUS\:.*//g')
+      elif [ "$DOWNLOAD_TOOL" = "wget" ]; then
+        TMP_FILE=$(mktemp)
+        BODY=$(wget --server-response --content-on-error -q -O - "$LATEST_RELEASE_URL" 2>"$TMP_FILE" || true)
+        HTTP_STATUS_CODE=$(awk '/^  HTTP/{print $2}' "$TMP_FILE")
+      fi
+      if [ "$HTTP_STATUS_CODE" != 200 ]; then
+        echo "Request failed with HTTP status code $HTTP_STATUS_CODE"
+        fail "Body: $BODY"
+      fi
+
+      # || true forces this command to not catch error if grep does not find anything
+      DOWNLOAD_URL=$(echo "$BODY" | grep 'browser_' | cut -d\" -f4 | grep "$APPLICATION_DIST") || true
+      if [ -z "$DOWNLOAD_URL" ]; then
+        DOWNLOAD_URL=$(echo "$BODY" | grep 'browser_' | cut -d\" -f4 | grep "$FALLBACK_APPLICATION_DIST") || true
+      fi
+
+      if [ -z "$DOWNLOAD_URL" ]; then
+        echo "Sorry, we dont have a dist for your system: $OS $ARCH"
+        fail "You can request one here: https://github.com/${PROJECT_OWNER}/$PROJECT_NAME/issues"
+      else
+        echo "Downloading $DOWNLOAD_URL"
+        getFile "$DOWNLOAD_URL" "$INSTALLATION_TMP_FILE"
+      fi
     fi
   fi
 }
@@ -208,6 +235,7 @@ initDestination
 set -e
 initArch
 initOS
+initFallbackArch
 initDownloadTool
 downloadFile "$1"
 installFile