zipl: copy new section introduced by GCC 9

GCC 9 is using a new section called .rodata.cst8 for some literals and
it must be included when copying the bootloaders to the bin images.

Closes: #60
Signed-off-by: Dan Horák <dan@danny.cz>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zipl/boot/Makefile

@@ -71,6 +71,7 @@ stage3.exec: head.o stage3.o kdump3.o libc.o sclp.o sclp_stage3.o \
 		--only-section=.ex_table \
 		--only-section=.data \
 		--only-section=.rodata.str1.2 \
+		--only-section=.rodata.cst8 \
 		--only-section=.rodata \
 		--only-section=.stage2dump.tail \
 		--only-section=.eckd2dump_mv.tail \