libffi: fix autotools scripts to respect libdir and includedir

configure flags.

src/libffi/configure.ac

@@ -601,11 +601,11 @@ if test "x$GCC" = "xyes"; then
     toolexecdir="${libdir}"/gcc-lib/'$(target_alias)'
     toolexeclibdir="${libdir}"
   fi
-  multi_os_directory=`$CC $CFLAGS -print-multi-os-directory`
-  case $multi_os_directory in
-    .) ;; # Avoid trailing /.
-    ../*) toolexeclibdir=$toolexeclibdir/$multi_os_directory ;;
-  esac
+  dnl multi_os_directory=`$CC $CFLAGS -print-multi-os-directory`
+  dnl case $multi_os_directory in
+  dnl   .) ;; # Avoid trailing /.
+  dnl   ../*) toolexeclibdir=$toolexeclibdir/$multi_os_directory ;;
+  dnl esac
   AC_SUBST(toolexecdir)
 else
   toolexeclibdir="${libdir}"

src/libffi/include/Makefile.am

@@ -5,5 +5,5 @@ AUTOMAKE_OPTIONS=foreign
 DISTCLEANFILES=ffitarget.h
 EXTRA_DIST=ffi.h.in ffi_common.h
 
-includesdir = $(libdir)/@PACKAGE_NAME@-@PACKAGE_VERSION@/include
+includesdir = $(includedir)
 nodist_includes_HEADERS = ffi.h ffitarget.h

src/libffi/libffi.pc.in

@@ -2,7 +2,7 @@ prefix=@prefix@
 exec_prefix=@exec_prefix@
 libdir=@libdir@
 toolexeclibdir=@toolexeclibdir@
-includedir=${libdir}/@PACKAGE_NAME@-@PACKAGE_VERSION@/include
+includedir=@includedir@
 
 Name: @PACKAGE_NAME@
 Description: Library supporting Foreign Function Interfaces