Updata ninja to v1.7.2.

New binaries for Mac, Linux32, Linux64, Windows.  Also update shell script.
See the bug for how these were built.
The main "new" thing is a regression fix where 1.7.1 broke %e %r in
NINJA_STATUS.

BUG=663749

Review-Url: https://codereview.chromium.org/2489023002

ninja

@@ -12,7 +12,7 @@ cat <<-EOF
 No prebuilt ninja binary was found for this system.
 Try building your own binary by doing:
   cd ~
-  git clone https://github.com/martine/ninja.git -b v1.7.1
+  git clone https://github.com/martine/ninja.git -b v1.7.2
   cd ninja && ./configure.py --bootstrap
 Then add ~/ninja/ to your PATH.
 EOF