Makefile: remove DESTDIR from firmware file content

The resulting firmware files should only contain the runtime path.
Fixes commit 26ce90fde5 ("Makefile: install the edk2 firmware images
and their descriptors")

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190530192812.17637-1-olaf@aepfle.de>
Fixes: https://bugs.launchpad.net/qemu/+bug/1838703
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Makefile

@@ -881,7 +881,7 @@ ifneq ($(DESCS),)
 	$(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)/firmware"
 	set -e; tmpf=$$(mktemp); trap 'rm -f -- "$$tmpf"' EXIT; \
 	for x in $(DESCS); do \
-		sed -e 's,@DATADIR@,$(DESTDIR)$(qemu_datadir),' \
+		sed -e 's,@DATADIR@,$(qemu_datadir),' \
 			"$(SRC_PATH)/pc-bios/descriptors/$$x" > "$$tmpf"; \
 		$(INSTALL_DATA) "$$tmpf" \
 			"$(DESTDIR)$(qemu_datadir)/firmware/$$x"; \