Add UT cases for exprtk functions related to nan

Add unit test cases for below exprtk functions:
* maxIgnoreNaN
* sumIgnoreNaN
* ifNan

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I4a9ea4b1f88ad1fd76295f88778a5bfc6b4defd1
diff --git a/meson.options b/meson.options
new file mode 100644
index 0000000..0fc2767
--- /dev/null
+++ b/meson.options
@@ -0,0 +1 @@
+option('tests', type: 'feature', description: 'Build tests')