Move unit tests to the location Meson expects them to be

Everything that is a separate subproject should live in the subprojects
directory.

Progress on #2503

This reverts commit 451f8a8c19.

src/libutil-tests/meson.build

@@ -0,0 +1,100 @@
+project('nix-util-tests', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+  dependency('nix-util-c'),
+  dependency('nix-util-test-support'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/threads')
+
+subdir('build-utils-meson/export-all-symbols')
+
+rapidcheck = dependency('rapidcheck')
+deps_private += rapidcheck
+
+gtest = dependency('gtest', main : true)
+deps_private += gtest
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+  '-include', 'config-util.hh',
+  '-include', 'config-util.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'args.cc',
+  'canon-path.cc',
+  'checked-arithmetic.cc',
+  'chunked-vector.cc',
+  'closure.cc',
+  'compression.cc',
+  'config.cc',
+  'executable-path.cc',
+  'file-content-address.cc',
+  'file-system.cc',
+  'git.cc',
+  'hash.cc',
+  'hilite.cc',
+  'json-utils.cc',
+  'logging.cc',
+  'lru-cache.cc',
+  'nix_api_util.cc',
+  'pool.cc',
+  'position.cc',
+  'processes.cc',
+  'references.cc',
+  'spawn.cc',
+  'strings.cc',
+  'suggestions.cc',
+  'terminal.cc',
+  'url.cc',
+  'util.cc',
+  'xml-writer.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+
+this_exe = executable(
+  meson.project_name(),
+  sources,
+  dependencies : deps_private_subproject + deps_private + deps_other,
+  include_directories : include_dirs,
+  # TODO: -lrapidcheck, see ../libutil-support/build.meson
+  link_args: linker_export_flags + ['-lrapidcheck'],
+  # get main from gtest
+  install : true,
+)
+
+test(
+  meson.project_name(),
+  this_exe,
+  env : {
+    '_NIX_TEST_UNIT_DATA': meson.current_source_dir() / 'data',
+  },
+  protocol : 'gtest',
+)