autoconf: Set LLVM_CONFIGTIME to a stable value when using --disable-timestamps.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151921 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/configure b/configure
index a65e9e4..a6ed7a1 100755
--- a/configure
+++ b/configure
@@ -20820,6 +20820,10 @@
 
 
 
+if test "${ENABLE_TIMESTAMPS}" = "0"; then
+  LLVM_CONFIGTIME="(timestamp not enabled)"
+fi
+
 
 cat >>confdefs.h <<_ACEOF
 #define LLVM_PREFIX "$LLVM_PREFIX"