grub-efi-native: Add support for EFI ISO images

The iso9660 file system support needs to be added to grub in order to
be able to correctly find the grub.cfg.  The grub commands to locate
the grub.cfg also needs to be encoded into grub's default
configuration.

This change allows the resulting grub binary to work both in the hard
drive / USB boot case or the optical media boot case.

[YOCTO #4100]

(From OE-Core rev: 0bc0762a479b5182a07fccb2b1e9cd5fc15ca485)

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-bsp/grub/files/cfg

@@ -0,0 +1,2 @@
+search.file /EFI/BOOT/grub.cfg root
+set prefix=($root)/EFI/BOOT

meta/recipes-bsp/grub/grub-efi-native_2.00.bb

@@ -23,6 +23,7 @@ PR = "r2"
 PN := "grub-efi-${TRANSLATED_TARGET_ARCH}-native"
 
 SRC_URI = "ftp://ftp.gnu.org/gnu/grub/grub-${PV}.tar.gz \
+           file://cfg \
            file://grub-2.00-fpmath-sse-387-fix.patch \
            file://grub-2.00-fix-enable_execute_stack-check.patch \
            file://grub-2.00-disable-help2man.patch \
@@ -66,9 +67,11 @@ EXTRA_OECONF = "--with-platform=efi --disable-grub-mkfont \
                 --enable-liblzma=no --enable-device-mapper=no --enable-libzfs=no"
 
 do_mkimage() {
-	./grub-mkimage -p /EFI/BOOT -d ./grub-core/ \
+	# Search for the grub.cfg on the local boot media by using the
+	# built in cfg file provided via this recipe
+	./grub-mkimage -c ../cfg -p /EFI/BOOT -d ./grub-core/ \
 	               -O ${GRUB_TARGET}-efi -o ./${GRUB_IMAGE} \
-	               boot linux ext2 fat serial part_msdos part_gpt normal efi_gop
+	               boot linux ext2 fat serial part_msdos part_gpt normal efi_gop iso9660 search
 }
 addtask mkimage after do_compile before do_install