[LIT] NFC adding max-failures option to lit documentation.

Differential Revision: https://reviews.llvm.org/D81337
diff --git a/llvm/docs/CommandGuide/lit.rst b/llvm/docs/CommandGuide/lit.rst
index 4fad853..dfc079e 100644
--- a/llvm/docs/CommandGuide/lit.rst
+++ b/llvm/docs/CommandGuide/lit.rst
@@ -158,6 +158,13 @@
 SELECTION OPTIONS
 -----------------
 
+.. option:: --max-failures MAX_FAILURES
+
+ Stop execution after the given number of failures.
+ An integer argument may be passed on the command line
+ or the environment vairable MAX_FAILURES may be set
+ prior to execution.
+
 .. option:: --max-tests=N
 
  Run at most ``N`` tests and then terminate.