meson: add necessary subprojects

Add subprojects for all the direct dependencies of the project such
that the project can be built outside of a Yocto SDK on a typical
Linux development system.

  - Update the .gitignore to ignore the subproject source directories.
  - Update the .gitignore to ignore alternative build subdirectory
    names as is typical with most projects in the openbmc organization.
  - Add wrap files for direct dependencies, copied from other
    repositories that already have the same dependencies.
  - Modify the meson.build dependency for libgpiod so that the C++
    bindings are included.
  - Add many missing dependencies throughout.
  - Sort all dependencies alphabetically for consistency.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I0feb6f0f175e6dba0b00a2c2b666eb0801575734
diff --git a/phosphor-regulators/test/meson.build b/phosphor-regulators/test/meson.build
index 3dc46f4..b290cd0 100644
--- a/phosphor-regulators/test/meson.build
+++ b/phosphor-regulators/test/meson.build
@@ -63,7 +63,10 @@
                 dependencies: [
                     gmock,
                     gtest,
-                    sdbusplus
+                    nlohmann_json_dep,
+                    phosphor_dbus_interfaces,
+                    phosphor_logging,
+                    sdbusplus,
                 ],
                 link_args: dynamic_linker,
                 build_rpath: get_option('oe-sdk').enabled() ? rpath : '',