check for pkg-config's m4 macros at bootstrap

bootstrap

@@ -47,13 +47,15 @@ SAGE_SPKG_CONFIGURE_$(echo ${pkgname} | tr '[a-z]' '[A-Z]')"
     case $st in
         0) true;; # Success
 
-        63|127)  # Autotools not installed or version too old
+        1|63|127)  # no m4 for pkg-config, or autotools not installed, or version too old
             if [ $DOWNLOAD = yes ]; then
                 echo >&2 "Bootstrap failed, downloading required files instead."
                 bootstrap-download || exit $?
             else
                 if [ $st -eq 127 ]; then
                     verb="install"
+                elif [ $st -eq 1 ]; then
+                    verb="install pkg-config m4 macros for"
                 else
                     verb="upgrade"
                 fi

build/pkgs/libffi/spkg-configure.m4

@@ -1,9 +1,5 @@
 SAGE_SPKG_CONFIGURE([libffi], [
-    dnl First try checking for libffi with pkg-config
-    PKG_CHECK_MODULES([LIBFFI], [libffi], [], [
-        dnl Fallback to manually grubbing around for headers and libs
-        AC_CHECK_HEADERS([ffi/ffi.h ffi.h], [sage_spkg_install_libffi=no; break], [sage_spkg_install_libffi=yes])
-        AC_SEARCH_LIBS([ffi_call], [ffi], [], [sage_spkg_install_libffi=yes])
-    ])
+    AC_SEARCH_LIBS([ffi_call], [ffi], [], [sage_spkg_install_libffi=yes])
+    AC_CHECK_HEADERS([ffi.h ffi/ffi.h], [break], [sage_spkg_install_libffi=yes])
 ])
 

configure.ac

@@ -216,6 +216,15 @@ then
     AC_MSG_ERROR([Exiting, as the macro processor 'm4' can not be found.])
 fi
 
+m4_ifndef([PKG_PROG_PKG_CONFIG],
+    [m4_fatal([Could not locate the pkg-config autoconf macros.
+    These are usually located in /usr/share/aclocal/pkg.m4. If your
+    macros are in a different location, try setting the environment
+    variable ACLOCAL="aclocal -I/other/macro/dir" before running
+    ./bootstrap])])
+
+PKG_PROG_PKG_CONFIG
+
 AC_CHECK_PROG(found_ranlib, ranlib, yes, no)
 if test x$found_ranlib != xyes
 then