Ensure that CMake is in the path on Windows.

Change-Id: Idc54e26dac243c0b354ec55759b8f87ed83af083
Reviewed-on: https://code-review.googlesource.com/c/re2/+/44226
Reviewed-by: Paul Wankadia <junyer@google.com>
diff --git a/kokoro/cmake.sh b/kokoro/cmake.sh
index bee1943..2d63a43 100755
--- a/kokoro/cmake.sh
+++ b/kokoro/cmake.sh
@@ -5,6 +5,7 @@
 
 case "${KOKORO_JOB_NAME}" in
   */windows-*)
+    export PATH+=';C:\Program Files\CMake\bin'
     # Pin to Visual Studio 2015, which is the minimum that we support.
     CMAKE_G_A_FLAGS=('-G' 'Visual Studio 14 2015' '-A' 'x64')
     ;;