cmake is used to build gtest and libevhtp

Change-Id: I1c81bbfbf275b27c6039d06555c6b22a2d9ec26a
Reviewed-on: https://weave-review.googlesource.com/2484
Reviewed-by: Jacob Marble <jacobmarble@google.com>

README.md

diff --git a/README.md b/README.md
index 211033c..6151061 100644
--- a/README.md
+++ b/README.md
@@ -77,11 +77,13 @@
 
 ### For tests
 
+  - cmake
   - gtest (included; see third_party/get_gtest.sh)
   - gmock (included; see third_party/get_gtest.sh)
 
 ### For examples
 
+  - cmake
   - hostapd
   - libavahi-client-dev
   - libcurl4-openssl-dev

examples/prerequisites.sh

diff --git a/examples/prerequisites.sh b/examples/prerequisites.sh
index 489bb58..4a019db 100755
--- a/examples/prerequisites.sh
+++ b/examples/prerequisites.sh
@@ -13,6 +13,7 @@
   autoconf \
   automake \
   binutils \
+  cmake \
   g++ \
   hostapd \
   libavahi-client-dev \