IBM Z: zTPF: Build libgcc with -mtpf-trace-skip

libgcc is supposed to be built with the trace skip flags and branch
targets.  Add a zTPF header file fragment and add the -mtpf-trace-skip
option.

libgcc/ChangeLog:

2020-03-04  Andreas Krebbel  <krebbel@linux.ibm.com>

	* config.host: Include the new makefile fragment.
	* config/s390/t-tpf: New file.

libgcc/config.host

@@ -1301,7 +1301,7 @@ s390x-*-linux*)
 	md_unwind_header=s390/linux-unwind.h
 	;;
 s390x-ibm-tpf*)
-	tmake_file="${tmake_file} s390/t-crtstuff t-libgcc-pic t-eh-dw2-dip"
+	tmake_file="${tmake_file} s390/t-crtstuff t-libgcc-pic t-eh-dw2-dip s390/t-tpf"
 	extra_parts="crtbeginS.o crtendS.o"
 	md_unwind_header=s390/tpf-unwind.h
 	;;

libgcc/config/s390/t-tpf

+DFP_ENABLE = true
+
+# Override t-slibgcc-elf-ver to export some libgcc symbols with
+# the symbol versions that glibc used.
+SHLIB_MAPFILES = libgcc-std.ver $(srcdir)/config/s390/libgcc-glibc.ver
+
+HOST_LIBGCC2_CFLAGS += -mlong-double-128 -mtpf-trace-skip