add "rocky" as a known distro using rpm

Summary:
X-link: facebookincubator/zstrong#746

this allows us to use the preinstalled package on a "rocky" box
as the build dependencies.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>

X-link: facebook/folly#1741

Reviewed By: dmm-fb

Differential Revision: D35348932

Pulled By: yfeldblum

fbshipit-source-id: 956cd6a7a8ddeffb090ef0c141feb5b946368e0d

build/fbcode_builder/getdeps/platform.py

@@ -270,7 +270,7 @@ def get_package_manager(self):
             return None
         if self.is_darwin():
             return "homebrew"
-        if self.distro in ("fedora", "centos", "centos_stream"):
+        if self.distro in ("fedora", "centos", "centos_stream", "rocky"):
             return "rpm"
         if self.distro.startswith(("debian", "ubuntu", "pop!_os")):
             return "deb"