Add -l flag when using lz4 compression

This isn't documented, but it's needed since the kernel lz4 support is
based on the original streaming format and not the newer default. Use
-l to force the legacy codec.

Fixup lsinitcpio to support the older format, and, add a warning when
the newer format is detected. Who knows when this will be "resolved" ...

Upstream discussion: https://code.google.com/p/lz4/issues/detail?id=102

lsinitcpio

@@ -91,10 +91,17 @@ detect_filetype() {
         return
     fi
 
-    if [[ $(hexdump -n 4 -e '"%x"' "$1") == '184d2204' ]]; then
-        echo 'lz4'
-        return
-    fi
+    case $(hexdump -n 4 -e '"%x"' "$1") in
+        184d2204)
+            error 'Newer lz4 stream format detected! This may not boot!'
+            echo 'lz4'
+            return
+            ;;
+        184c2102)
+            echo 'lz4 -l'
+            return
+            ;;
+    esac
 
     if [[ $(hexdump -n 3 -e '"%c"' "$1") == 'BZh' ]]; then
         echo 'bzip2'

mkinitcpio

@@ -202,6 +202,9 @@ build_image() {
         xz)
             COMPRESSION_OPTIONS+=' --check=crc32'
             ;;
+        lz4)
+            COMPRESSION_OPTIONS+=' -l'
+            ;;
     esac
 
     cpio_opts=('-0' '-o' '-H' 'newc')