Fix build failure with zstd versio9n 1.2.0 or older.

Extends the configure check for zstd.h to also verify the zstd version,
since gcc requires features that only exist in 1.3.0 and newer.  Without
this patch we get a build error for lto-compress.c when using an old zstd
version.

	Backported from master:
	2020-09-29  Jim Wilson  <jimw@sifive.com>

	gcc/
	PR bootstrap/97183
	* configure.ac (gcc_cv_header_zstd_h): Check ZSTD_VERISON_NUMBER.
	* configure: Regenerated.

Author: Jim Wilson

gcc/configure

@@ -10024,9 +10024,14 @@ $as_echo_n "checking for zstd.h... " >&6; }
 if ${gcc_cv_header_zstd_h+:} false; then :
   $as_echo_n "(cached) " >&6
 else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+  # We require version 1.3.0 or later.  This is the first version that has
+# ZSTD_getFrameContentSize.
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <zstd.h>
+#if ZSTD_VERSION_NUMBER < 10300
+#error "need zstd 1.3.0 or better"
+#endif
 int
 main ()
 {
@@ -19015,7 +19020,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 19018 "configure"
+#line 19023 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -19121,7 +19126,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 19124 "configure"
+#line 19129 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H

gcc/configure.ac

@@ -1382,8 +1382,13 @@ LDFLAGS="$LDFLAGS $ZSTD_LDFLAGS"
 
 AC_MSG_CHECKING(for zstd.h)
 AC_CACHE_VAL(gcc_cv_header_zstd_h,
+# We require version 1.3.0 or later.  This is the first version that has
+# ZSTD_getFrameContentSize.
 [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
-[[#include <zstd.h>]])],
+[[#include <zstd.h>
+#if ZSTD_VERSION_NUMBER < 10300
+#error "need zstd 1.3.0 or better"
+#endif]])],
   [gcc_cv_header_zstd_h=yes],
   [gcc_cv_header_zstd_h=no])])
 AC_MSG_RESULT($gcc_cv_header_zstd_h)