mononoke/fbcode_builder: bring back mononoke manifests for getdeps build

Summary:
The breakage has been fixed, so bring back the manifest, but only the Linux one, because the Mac version is failing due to another issue.

Also to make it easier to debug issues on GitHub Actions separate out the dependencies build from Mononoke and rust-shed builds.

Reviewed By: krallin

Differential Revision: D21448412

fbshipit-source-id: 68d89c858d1692727a7fd66bca114920e6dfb4dc

build/fbcode_builder/getdeps.py

@@ -468,7 +468,12 @@ class BuildCmd(ProjectCmdBase):
             build_dir = loader.get_project_build_dir(m)
             inst_dir = loader.get_project_install_dir(m)
 
-            if m == manifest or not args.no_deps:
+            if (
+                m == manifest
+                and not args.only_deps
+                or m != manifest
+                and not args.no_deps
+            ):
                 print("Assessing %s..." % m.name)
                 project_hash = loader.get_project_hash(m)
                 ctx = loader.ctx_gen.get_context(m.name)
@@ -610,6 +615,16 @@ class BuildCmd(ProjectCmdBase):
                 "slow up-to-date-ness checks"
             ),
         )
+        parser.add_argument(
+            "--only-deps",
+            action="store_true",
+            default=False,
+            help=(
+                "Only build the named project's deps. "
+                "This is most useful when you want to separate out building "
+                "of all of the deps and your project"
+            ),
+        )
         parser.add_argument(
             "--no-build-cache",
             action="store_false",