lottie/example: disable default building of example

to enable use meson -Dexample=true build while configuring meson.
or meson configure -Dexample=true in the build directory.

Change-Id: If267e6883fb866a741bf18dbfedd2a7782e21df5

README.txt

@@ -2,10 +2,13 @@ BUILD INSTRUCTION
 =================
 1. install meson build system. ( follow instruction in this link http://mesonbuild.com/Getting-meson.html )
 2. install ninja build tool    (https://ninja-build.org/)
-3. make a build directory in ssg/ flder
-4. run meson build/
+4. invoke meson build/  or meson -Dexample=true build/
+5. invoke ninja inside the build folder.
 
-RUN INSTRUCTION
+NOTE: run meson configure to see all the build options
+
+BUILD EXAMPLE
 ===============
-1. run ninja inside build/ folder
-2. to run example invoke ./build/example/ssgdemo
+1. meson configure -Dexample=true
+2. ninja
+3. to run example invoke ./build/example/demo

meson.build

@@ -20,7 +20,9 @@ inc = include_directories('inc')
 subdir('inc')
 subdir('src')
 
-subdir('example')
+if get_option('example') == true
+    subdir('example')
+endif
 
 if get_option('test') == true
    subdir('test')

meson_options.txt

@@ -5,7 +5,7 @@ option('test',
 
 option('example',
    type: 'boolean',
-   value: true,
+   value: false,
    description: 'enable example')
 
 option('text',