Add unit test for common/buf.c

t/meson.build

@@ -0,0 +1,27 @@
+test_lib = static_library(
+  'test_lib',
+  sources: files(
+    '../src/common/buf.c',
+    '../src/common/mem.c',
+    '../src/common/string-helpers.c'
+  ),
+  include_directories: [labwc_inc],
+  dependencies: [dep_cmocka],
+)
+
+tests = [
+  'buf-simple',
+]
+
+foreach t : tests
+  test(
+    'test_@0@'.format(t),
+    executable(
+      'test_@0@'.format(t),
+      sources: '@0@.c'.format(t),
+      include_directories: [labwc_inc],
+      link_with: [test_lib],
+    ),
+    is_parallel: false,
+  )
+endforeach