Make --disable-libffi work on systems with libffi installed.  Also
make no-ffi the default even on systems with libffi.  This fixes
http://llvm.org/PR5018.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@95712 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index a534866..40f77d8 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -727,13 +727,13 @@
 
 dnl --enable-libffi : check whether the user wants to turn off libffi:
 AC_ARG_ENABLE(libffi,AS_HELP_STRING(
-  --enable-libffi,[Check for the presence of libffi (default is YES)]),,
-  enableval=yes)
-case "$enableval" in
-  yes) llvm_cv_enable_libffi="yes" ;;
-  no)  llvm_cv_enable_libffi="no"  ;;
-  *) AC_MSG_ERROR([Invalid setting for --enable-libffi. Use "yes" or "no"]) ;;
-esac
+  --enable-libffi,[Check for the presence of libffi (default is NO)]),
+  [case "$enableval" in
+    yes) llvm_cv_enable_libffi="yes" ;;
+    no)  llvm_cv_enable_libffi="no"  ;;
+    *) AC_MSG_ERROR([Invalid setting for --enable-libffi. Use "yes" or "no"]) ;;
+  esac],
+  llvm_cv_enable_libffi=no)
 
 dnl Only Windows needs dynamic libCompilerDriver to support plugins.
 if test "$llvm_cv_os_type" = "Win32" ; then
@@ -1021,7 +1021,7 @@
 if test "$llvm_cv_enable_libffi" = "yes" ; then
   AC_SEARCH_LIBS(ffi_call,ffi,AC_DEFINE([HAVE_FFI_CALL],[1],
                  [Define if libffi is available on this platform.]),
-                 AC_MSG_WARN([libffi not found - disabling external calls from interpreter]))
+                 AC_MSG_ERROR([libffi not found - configure without --enable-libffi to compile without it]))
 fi
 
 dnl mallinfo is optional; the code can compile (minus features) without it