check for isatty function

llvm-svn: 12635
diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index 49010c4..3a3dfd8 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -282,7 +282,7 @@
 fi
 AC_HEADER_MMAP_ANONYMOUS
 AC_TYPE_SIGNAL
-AC_CHECK_FUNCS(getcwd gettimeofday strdup strtoq strtoll backtrace)
+AC_CHECK_FUNCS(getcwd gettimeofday strdup strtoq strtoll backtrace isatty)
 AC_CHECK_FUNC(mprotect,,AC_MSG_ERROR([Function mprotect() required but not found]))
 
 dnl Determine if the linker supports the -R option.