tests: Mock libfeedback

Copied from libfeedback as of 2e081602f627505e566cc0bdb6cd96c7642d8b65
and adjusted for our mocking needs.

The mocked library will be LD_PRELOADED for the moment,
but further changes to the build should allow us to simply link
to it in the future.

tests/mock/lfb/meson.build

@@ -0,0 +1,52 @@
+libfeedback_libdir = get_option('libdir')
+libfeedback_link_args = []
+libfeedback_symbols_file = 'libfeedback.syms'
+
+lfb_enum_headers = files([
+  'lfb-event.h',
+])
+
+libfeedback_headers = [
+  'libfeedback.h',
+  'lfb-event.h',
+]
+
+libfeedback_sources = [
+  'lfb-enums.c',
+  libfeedback_headers,
+  'libfeedback.c',
+  'lfb-event.c',
+]
+
+gio            = dependency('gio-2.0', version: '>=2.50.0')
+glib           = dependency('glib-2.0', version: '>=2.50.0')
+gobject        = dependency('gobject-2.0', version: '>=2.50.0')
+
+libfeedback_deps = [
+  gio,
+  glib,
+  gobject,
+]
+
+libfeedback_c_args = [
+  '-DG_LOG_DOMAIN="libfeedback"',
+]
+
+libtype = 'shared_library'
+libfeedback = build_target(
+  'feedback-0',
+  libfeedback_sources,
+            soversion : 0,
+               c_args : libfeedback_c_args,
+         dependencies : libfeedback_deps,
+            link_args : [],
+              install : false,
+          target_type : libtype,
+)
+
+libfeedback_inc = include_directories('.')
+libfeedback_dep = declare_dependency(
+  link_with : libfeedback,
+  dependencies: libfeedback_deps,
+  include_directories : libfeedback_inc,
+)