Enable tests, fixing the existing ones to use the current API

This also involved building a static library for the application for
tests to link to. The main application executable also links to it.

tests/meson.build

@@ -0,0 +1,49 @@
+if get_option('tests')
+
+test_env = [
+  'G_TEST_SRCDIR=@0@'.format(meson.current_source_dir()),
+  'G_TEST_BUILDDIR=@0@'.format(meson.current_build_dir()),
+  'G_DEBUG=gc-friendly,fatal-warnings',
+  'GSETTINGS_BACKEND=memory',
+  'MALLOC_CHECK_=2'
+]
+
+test_cflags = [
+  '-I@0@/../src'.format(meson.current_source_dir()),
+  '-I@0@/../src'.format(meson.current_build_dir()),
+  '-DEEK_COMPILATION',
+  '-DEEKBOARD_COMPILATION'
+]
+
+test_link_args = [
+  '-fPIC',
+]
+
+tests = [
+  'eek-simple-test',
+  'eek-xml-test'
+]
+
+foreach name : tests
+
+    test_sources = [name + '.c']
+
+    t = executable(
+        name,
+        test_sources,
+        squeekboard_resources,
+        link_with: libsqueekboard,
+        c_args : test_cflags,
+        link_args: test_link_args,
+        dependencies: deps,       # from src/meson.build
+        include_directories: [
+            include_directories('..'),
+            include_directories('../eek')
+        ]
+    )
+
+    test(name, t, env: test_env)
+
+endforeach
+
+endif