build: Add meson support

Add support for buildling with meson.

Support for --enable-oe-sdk is dropped because running unit tests on the
build system is now supported directly with meson subprojects:

meson buildir && ninja -C buildir test

I tested this by building a witherspoon image and booting it to
multi-user and verifying the mapper-wait functionality works correctly.

Change-Id: I86e5efc7b7c89183219a4c890ad658e334765fc1
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meson_options.txt b/meson_options.txt
new file mode 100644
index 0000000..cdf492c
--- /dev/null
+++ b/meson_options.txt
@@ -0,0 +1 @@
+option('tests', type: 'feature', description: 'Build tests', value: 'enabled')