Update doc/help to say --ninja-executable works for VS Flags

Change-Id: I63aa2f9f262849dab395c9621e41069b1ee93e25
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/11920
Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>

docs/reference.md

diff --git a/docs/reference.md b/docs/reference.md
index ddf73e6..9104076 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -804,6 +804,9 @@
       As an example, "10.0.15063.0" can be specified to use Creators Update SDK
       instead of the default one.
 
+  --ninja-executable=<string>
+      Can be used to specify the ninja executable to use when building.
+
   --ninja-extra-args=<string>
       This string is passed without any quoting to the ninja invocation
       command-line. Can be used to configure ninja flags, like "-j".

src/gn/command_gen.cc

diff --git a/src/gn/command_gen.cc b/src/gn/command_gen.cc
index 0f4ed70..e391d26 100644
--- a/src/gn/command_gen.cc
+++ b/src/gn/command_gen.cc
@@ -493,6 +493,9 @@
       As an example, "10.0.15063.0" can be specified to use Creators Update SDK
       instead of the default one.
 
+  --ninja-executable=<string>
+      Can be used to specify the ninja executable to use when building.
+
   --ninja-extra-args=<string>
       This string is passed without any quoting to the ninja invocation
       command-line. Can be used to configure ninja flags, like "-j".