Extend/fix support for extlinux bootloader

Some extlinux packages install mbr.bin under /usr/lib/extlinux or
/usr/lib/EXTLINUX so tese directories need to be checked as well.
Also, there are packages that create a /boot/extlinux directory
which needs to be taken into account. Finally, commit
bccffc8bfd dropped the /boot prefix
from the kernel and initrd references in the ext/syslinux config
file which is simply a bug that needs fixing.

Change-Id: Idb071c9b18ff557b0f0f76d0d754536f2deca904
Closes-Bug: 1335042

elements/vm/cleanup.d/51-bootloader

@@ -22,16 +22,22 @@ set -o pipefail
 
 source $_LIB/img-functions
 
-# Dig up the initrd and kernel to use.
-if [ -d $TARGET_ROOT/boot/syslinux ] ; then
-    select_boot_kernel_initrd $TARGET_ROOT
+if [ -d $TARGET_ROOT/boot/extlinux ] ; then
+    CONF=$TARGET_ROOT/boot/extlinux/extlinux.conf
+elif [ -d $TARGET_ROOT/boot/syslinux ] ; then
+    CONF=$TARGET_ROOT/boot/syslinux/syslinux.cfg
+else
+    exit 0
+fi
 
-    cat > $TARGET_ROOT/boot/syslinux/syslinux.cfg<<_EOF_
+# Dig up the initrd and kernel to use.
+select_boot_kernel_initrd $TARGET_ROOT
+
+sudo sh -c "cat > $CONF <<_EOF_
 DEFAULT linux
 
 LABEL linux
-    KERNEL $KERNEL
-    APPEND ro root=LABEL=cloudimg-rootfs console=tty0 console=ttyS0,115200
-    INITRD $RAMDISK
-_EOF_
-fi
+    KERNEL /boot/$KERNEL
+    APPEND ro root=LABEL=cloudimg-rootfs console=tty0 console=ttyS0,115200 nofb nomodeset vga=normal
+    INITRD /boot/$RAMDISK
+_EOF_"

elements/vm/finalise.d/51-bootloader

@@ -16,19 +16,34 @@ function install_extlinux {
 
     echo "Installing Extlinux..."
 
-    MBR=/usr/share/syslinux/mbr.bin
-    if [ ! -f $MBR ]; then
-        MBR=/usr/lib/syslinux/mbr.bin
-        if [ ! -f $MBR ]; then
-            echo "mbr.bin (from SYSLINUX) not found."
-            exit 1
+    # Find and install mbr.bin
+    for MBR in /usr/share/syslinux/mbr.bin /usr/lib/syslinux/mbr.bin \
+        /usr/lib/extlinux/mbr.bin /usr/lib/EXTLINUX/mbr.bin ; do
+        if [ -f $MBR ]; then
+            break
         fi
+    done
+    if [ ! -f $MBR ]; then
+        echo "mbr.bin (from EXT/SYSLINUX) not found."
+        exit 1
     fi
 
     dd if=$MBR of=$BOOT_DEV
 
-    mkdir -p /boot/syslinux
-    extlinux --install /boot/syslinux
+    # Find any pre-created extlinux install directory
+    for EXTDIR in /boot/extlinux /boot/syslinux ; do
+        if [ -d $EXTDIR ] ; then
+            break
+        fi
+    done
+    if [ ! -d $EXTDIR ] ; then
+        # No install directory found so default to /boot/syslinux
+        EXTDIR=/boot/syslinux
+        mkdir -p $EXTDIR
+    fi
+
+    # Finally install extlinux
+    extlinux --install $EXTDIR
 }
 
 function install_grub2 {