cmake: prefix host tools file names with optee_example_

Sync the CMake build with the GNU make and the Android make
process. All client applications generated by this package
are prefixed with optee_example_.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
diff --git a/hello_world/CMakeLists.txt b/hello_world/CMakeLists.txt
index 1b46b4c..937b8cf 100644
--- a/hello_world/CMakeLists.txt
+++ b/hello_world/CMakeLists.txt
@@ -1,4 +1,4 @@
-project (hello_world C)
+project (optee_example_hello_world C)
 
 set (SRC host/main.c)