[PATCH][linux-snap][bionic][master] Copy host trusted.gpg keyring only when it exists

[Wen-chien Jesse Sung]

The file may not be available when the snap doesn't build on Launchpad.

Signed-off-by: Wen-chien Jesse Sung <jesse.sung at canonical.com>
---
 Makefile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index f9137c0..7620b98 100644
--- a/Makefile
+++ b/Makefile
@@ -93,7 +93,9 @@ prepare-chroot:
 	cp /etc/apt/sources.list chroot/etc/apt/sources.list
 	echo "deb http://ppa.launchpad.net/snappy-dev/image/ubuntu $(RELEASE) main" >> chroot/etc/apt/sources.list
 	# Copy the host's trusted.gpg for ubuntu-esm repositories
-	cp /etc/apt/trusted.gpg chroot/etc/apt/trusted.gpg.d/host-trusted.gpg
+	if [ -f /etc/apt/trusted.gpg ]; then \
+		cp /etc/apt/trusted.gpg chroot/etc/apt/trusted.gpg.d/host-trusted.gpg; \
+	fi
 
 	# install all updates
 	$(ENV) chroot chroot apt-get -y update
-- 
2.30.2