Support of Arch Linux in getdeps.py

Summary:
X-link: https://github.com/facebookincubator/zstrong/pull/907

I don't sure that I make all in accordance with the your contribution pipeline, so please correct me If there is needed.
So, I've made some changes to support the `pacman` package manager in your `getdeps.py` script. In `manifests` I'm also duplicated some packages from `debs` and `rpms` sections and create a new `pps` sections with according packages for  `pacman`.

Issue:  https://github.com/facebook/folly/issues/1701

X-link: https://github.com/facebook/folly/pull/1702

Reviewed By: yfeldblum

Differential Revision: D33514769

Pulled By: Orvid

fbshipit-source-id: a081c3a5bcb7f7cdde3a4a91c0d15517c0a171b3

build/fbcode_builder/getdeps.py

@@ -370,7 +370,7 @@ class InstallSysDepsCmd(ProjectCmdBase):
         parser.add_argument(
             "--os-type",
             help="Filter to just this OS type to run",
-            choices=["linux", "darwin", "windows"],
+            choices=["linux", "darwin", "windows", "pacman-package"],
             action="store",
             dest="ostype",
             default=None,
@@ -440,7 +440,10 @@ class InstallSysDepsCmd(ProjectCmdBase):
             packages = sorted(set(all_packages["homebrew"]))
             if packages:
                 cmd_args = ["brew", "install"] + packages
-
+        elif manager == "pacman-package":
+            packages = sorted(list(set(all_packages["pacman-package"])))
+            if packages:
+                cmd_args = ["pacman", "-S"] + packages
         else:
             host_tuple = loader.build_opts.host_type.as_tuple_string()
             print(