Support downloading ACK kernels

Author: gsingh93

Makefile

@@ -180,7 +180,7 @@ linux_download:
 ifndef VERSION
 	$(error VERSION environment variable is not defined)
 endif
-	$(SCRIPT_DIR)/download_linux.sh $(VERSION)
+	$(SCRIPT_DIR)/download_linux.sh $(VERSION) $(ACK)
 
 .PHONY: linux_checkout
 linux_checkout:

scripts/download_linux.sh

@@ -3,26 +3,36 @@
 set -o errexit
 
 VERSION="$1"
+ACK="${2:-0}"
 MIN_VERSION=2
 MAX_VERSION=6
 
+LINUX_URL=https://cdn.kernel.org/pub/linux/kernel
+ACK_URL=https://android.googlesource.com/kernel/common/+archive/refs/heads
+
 if [ -z "$VERSION" ]; then
     echo "usage: $0 VERSION"
     exit 1
 fi
 
-first_char=${VERSION:0:1}
+if [ $ACK -eq 0 ]; then
+    first_char=${VERSION:0:1}
 
-if [ $first_char == v ]; then
-    VERSION=${VERSION:1}
-fi
+    if [ $first_char == v ]; then
+        VERSION=${VERSION:1}
+    fi
 
-first_char=${VERSION:0:1}
+    first_char=${VERSION:0:1}
 
-if [ $first_char -ge $MIN_VERSION ] && [ $first_char -le $MAX_VERSION ]; then
-    wget https://cdn.kernel.org/pub/linux/kernel/v${first_char}.x/linux-${VERSION}.tar.xz
-    tar -xf linux-${VERSION}.tar.xz
+    if [ $first_char -ge $MIN_VERSION ] && [ $first_char -le $MAX_VERSION ]; then
+        wget $LINUX_URL/v${first_char}.x/linux-$VERSION.tar.xz
+        tar -xf linux-$VERSION.tar.xz
+    else
+        echo "$first_char is not a valid kernel major version number"
+        exit 1
+    fi
 else
-    echo "$first_char is not a valid kernel major version number"
-    exit 1
+    wget $ACK_URL/$VERSION.tar.gz
+    mkdir -p $VERSION
+    tar -xf $VERSION.tar.gz -C $VERSION
 fi