linux-user, i386: add syscall table generation support

Copy syscall_32.tbl and syscallhdr.sh from linux/arch/x86/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: <20200310103403.3284090-15-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/configure b/configure
index 0f063c3..84bedad 100755
--- a/configure
+++ b/configure
@@ -1890,7 +1890,7 @@
 # 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 m68k xtensa sh4 microblaze arm ppc s390x sparc sparc64 \
-    ; do
+    i386 ; 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
@@ -7788,6 +7788,7 @@
   i386)
     mttcg="yes"
 	gdb_xml_files="i386-32bit.xml"
+    TARGET_SYSTBL_ABI=i386
   ;;
   x86_64)
     TARGET_BASE_ARCH=i386