linux-user, m68k: add syscall table generation support

Copy syscall.tbl and syscallhdr.sh from linux/arch/m68k/kernel/syscalls v5.5
Update syscallhdr.sh to generate QEMU syscall_nr.h

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20200310103403.3284090-5-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

configure

@@ -1889,7 +1889,7 @@ rm -f */config-devices.mak.d
 
 # Remove syscall_nr.h to be sure they will be regenerated in the build
 # directory, not in the source directory
-for arch in alpha hppa ; do
+for arch in alpha hppa m68k ; do
     # remove the file if it has been generated in the source directory
     rm -f "${source_path}/linux-user/${arch}/syscall_nr.h"
     # remove the dependency files
@@ -7821,6 +7821,7 @@ case "$target_name" in
   m68k)
     bflt="yes"
     gdb_xml_files="cf-core.xml cf-fp.xml m68k-fp.xml"
+    TARGET_SYSTBL_ABI=common
   ;;
   microblaze|microblazeel)
     TARGET_ARCH=microblaze

linux-user/Makefile.objs

@@ -11,3 +11,4 @@ obj-$(TARGET_AARCH64) += arm/semihost.o
 
 obj-$(TARGET_ALPHA) += alpha/
 obj-$(TARGET_HPPA) += hppa/
+obj-$(TARGET_M68K) += m68k/

linux-user/m68k/Makefile.objs

@@ -0,0 +1,5 @@
+generated-files-y += linux-user/m68k/syscall_nr.h
+
+syshdr := $(SRC_PATH)/linux-user/m68k/syscallhdr.sh
+%/syscall_nr.h: $(SRC_PATH)/linux-user/m68k/syscall.tbl $(syshdr)
+	$(call quiet-command, sh $(syshdr) $< $@ $(TARGET_SYSTBL_ABI),"GEN","$@")