[PATCH 1/2] Fix util/grub.d/20_linux_xen.in: Add xen_boot command support for aarch64

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Commit d33045ce7ffcb7c1e4a60c14d5ca64b36e3c5abe introduced
the support for this, but it does not work under x86 (as it stops
20_linux_xen from running).

The 20_linux_xen is run under a shell and any exits from within it:

(For example on x86):
+ /usr/bin/grub2-file --is-arm64-efi /boot/xen-4.9.0.gz
[root@tst063 grub]# echo $?
1

will result in 20_linux_xen exciting without continuing
and also causing grub2-mkconfig to stop processing.

As in:

[root@tst063 ~]#

And no more.

This patch wraps the invocation of grub-file to be a in subshell
and to process the return value in a conditional. That fixes
the issue.

RH-BZ 1486002: grub2-mkconfig does not work if xen.gz is installed.
CC: Fu Wei <fu.wei@linaro.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 util/grub.d/20_linux_xen.in | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/util/grub.d/20_linux_xen.in b/util/grub.d/20_linux_xen.in
index c002fc9..083bcef 100644
--- a/util/grub.d/20_linux_xen.in
+++ b/util/grub.d/20_linux_xen.in
@@ -206,13 +206,12 @@ while [ "x${xen_list}" != "x" ] ; do
     if [ "x$is_top_level" != xtrue ]; then
 	echo "	submenu '$(gettext_printf "Xen hypervisor, version %s" "${xen_version}" | grub_quote)' \$menuentry_id_option 'xen-hypervisor-$xen_version-$boot_device_id' {"
     fi
-    $grub_file --is-arm64-efi $current_xen
-    if [ $? -ne 0 ]; then
-	xen_loader="multiboot"
-	module_loader="module"
-    else
+    if ($grub_file --is-arm64-efi $current_xen); then
 	xen_loader="xen_hypervisor"
 	module_loader="xen_module"
+    else
+	xen_loader="multiboot"
+	module_loader="module"
     fi
     while [ "x$list" != "x" ] ; do
 	linux=`version_find_latest $list`
-- 
2.1.4