watchman: fixup FB internal mac packaging

Summary:
with the reshuffling around getdeps.py, and changes in folly/thrift/wangle,
our internal package stopped building.  This diff brings it back to life.  It is
a little bit interwined:

* Introduce a `--facebook-internal` switch to getdeps that causes `fb` in the
  build context to be set to `on` rather than `off`.  This allows specifying
  options in the manifest that are FB specific.
* Introduce cmake options to control the WATCHMAN_STATE_DIR and whether cmake
  should attempt to create WATCHMAN_STATE_DIR when it is installed.
* For FB specific builds on macOS, set the state dir to match our existing location
  and disable creation of WATCHMAN_STATE_DIR because that will ultimately be
  handling during package installation and we don't have privs for that on
  the machine generating the package.
* Adjust Facebook CI scripts to use getdeps for building and testing watchman

Reviewed By: simpkins

Differential Revision: D15337970

fbshipit-source-id: 8ab3c1f810decf5f0b16337dc1cbe6dc73d26426

build/fbcode_builder/getdeps.py

@@ -213,7 +213,7 @@ class BuildCmd(SubCmd):
 
         manifest = load_project(opts, args.project)
 
-        ctx = context_from_host_tuple()
+        ctx = context_from_host_tuple(facebook_internal=args.facebook_internal)
         print("Building on %s" % ctx)
         projects = manifests_in_dependency_order(opts, manifest, ctx)
         manifests_by_name = {m.name: m for m in projects}
@@ -313,7 +313,7 @@ class TestCmd(SubCmd):
         opts = setup_build_options(args)
         manifest = load_project(opts, args.project)
 
-        ctx = context_from_host_tuple()
+        ctx = context_from_host_tuple(facebook_internal=args.facebook_internal)
         ctx["test"] = "on"
         projects = manifests_in_dependency_order(opts, manifest, ctx)
         manifests_by_name = {m.name: m for m in projects}
@@ -388,6 +388,12 @@ def build_argparser():
         action="store_true",
         default=False,
     )
+    common_args.add_argument(
+        "--facebook-internal",
+        help="Setup the build context as an FB internal build",
+        action="store_true",
+        default=False,
+    )
 
     ap = argparse.ArgumentParser(
         description="Get and build dependencies and projects", parents=[common_args]