AK3: also ensure $comp fallback is a working command for ramdisks

META-INF/com/google/android/updater-script

@@ -3,4 +3,4 @@
 # Dummy file; update-binary is a shell script (DO NOT CHANGE)
 #
 #
-# AK_BASE_VERSION=20220403
+# AK_BASE_VERSION=20220410

tools/ak3-core.sh

@@ -160,7 +160,7 @@ unpack_ramdisk() {
   if [ "$comp" ]; then
     mv -f ramdisk.cpio ramdisk.cpio.$comp;
     $bin/magiskboot decompress ramdisk.cpio.$comp ramdisk.cpio;
-    if [ $? != 0 ]; then
+    if [ $? != 0 ] && $comp --help 2>/dev/null; then
       echo "Attempting ramdisk unpack with busybox $comp..." >&2;
       $comp -dc ramdisk.cpio.$comp > ramdisk.cpio;
     fi;
@@ -216,7 +216,7 @@ repack_ramdisk() {
   [ $((magisk_patched & 3)) -eq 1 ] && $bin/magiskboot cpio ramdisk-new.cpio "extract .backup/.magisk $split_img/.magisk";
   if [ "$comp" ]; then
     $bin/magiskboot compress=$comp ramdisk-new.cpio;
-    if [ $? != 0 ]; then
+    if [ $? != 0 ] && $comp --help 2>/dev/null; then
       echo "Attempting ramdisk repack with busybox $comp..." >&2;
       $comp -9c ramdisk-new.cpio > ramdisk-new.cpio.$comp;
       [ $? != 0 ] && packfail=1;