--- a/libgfortran/configure.ac	Thu Oct 25 07:37:49 2018 +0900
+++ b/libgfortran/configure.ac	Thu Feb 13 11:34:05 2020 +0900
@@ -1,7 +1,6 @@
 # Process this file with autoconf to produce a configure script, like so:
 # aclocal && autoconf && autoheader && automake
 
-AC_PREREQ(2.64)
 AC_INIT([GNU Fortran Runtime Library], 0.3,,[libgfortran])
 AC_CONFIG_HEADER(config.h)
 GCC_TOPLEV_SUBDIRS
@@ -87,6 +86,8 @@
 
 AC_USE_SYSTEM_EXTENSIONS
 
+GCC_WITH_TOOLEXECLIBDIR
+
 # Calculate toolexeclibdir
 # Also toolexecdir, though it's only used in toolexeclibdir
 case ${version_specific_libs} in
@@ -102,7 +103,14 @@
        test x"$with_cross_host" != x"no"; then
       # Install a library built with a cross compiler in tooldir, not libdir.
       toolexecdir='$(exec_prefix)/$(target_alias)'
-      toolexeclibdir='$(toolexecdir)/lib'
+      case ${with_toolexeclibdir} in
+	no)
+	  toolexeclibdir='$(toolexecdir)/lib'
+	  ;;
+	*)
+	  toolexeclibdir=${with_toolexeclibdir}
+	  ;;
+      esac
     else
       toolexecdir='$(libdir)/gcc-lib/$(target_alias)'
       toolexeclibdir='$(libdir)'
@@ -314,8 +322,8 @@
 else
    AC_CHECK_FUNCS_ONCE(getrusage times mkstemp strtof strtold snprintf \
    ftruncate chsize chdir getentropy getlogin gethostname kill link symlink \
-   sleep ttyname \
-   alarm access fork setmode fcntl writev \
+   sleep ttyname sigaction waitpid \
+   alarm access fork posix_spawn setmode fcntl writev \
    gettimeofday stat fstat lstat getpwuid vsnprintf dup \
    getcwd localtime_r gmtime_r getpwuid_r ttyname_r clock_gettime \
    getgid getpid getuid geteuid umask getegid \
@@ -609,8 +617,8 @@
 LIBGFOR_CHECK_ATTRIBUTE_VISIBILITY
 LIBGFOR_CHECK_ATTRIBUTE_ALIAS
 
-# Check out sync builtins support.
-LIBGFOR_CHECK_SYNC_FETCH_AND_ADD
+# Check out atomic builtins support.
+LIBGFOR_CHECK_ATOMIC_FETCH_ADD
 
 # Check out #pragma weak.
 LIBGFOR_GTHREAD_WEAK