Fix a problem in the target detection for Debian GNU/HURD



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154117 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index 7f4b25e..884a21b 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -300,6 +300,8 @@
     llvm_cv_target_os_type="Interix" ;;
   *-*-linux*)
     llvm_cv_target_os_type="Linux" ;;
+  *-*-gnu*)
+    llvm_cv_target_os_type="GNU" ;;
   *-*-solaris*)
     llvm_cv_target_os_type="SunOS" ;;
   *-*-auroraux*)