preserve http_proxy in generated github actions sudo invocatons

Summary:
X-link: https://github.com/facebookincubator/zstrong/pull/1102

make it possible to run the generated github actions locally with [act](https://github.com/nektos/act) when behind a proxy by preserving http_proxy in generated github actions sudo invocatons

also updated to consistently write `apt-get` instead of the interactive `apt` (we had a mix)

example usage (substitute myproxy for your actual proxy):
```
mkdir $HOME/act-artifacts
cd ~/fizz
time act -r -j build -W .github/workflows/getdeps_linux.yml --artifact-server-path=$HOME/act-artifacts --artifact-server-addr=127.0.0.1 --cache-server-addr=127.0.0.1 --env http_proxy=http://myproxy:8080 --env https_proxy=myproxy:8080 --action-offline-mode
```

Reviewed By: bigfootjon

Differential Revision: D67864689

fbshipit-source-id: 45695675ca5672e56104c8c33803afe004ff98da

build/fbcode_builder/getdeps.py

@@ -440,7 +440,13 @@ class InstallSysDepsCmd(ProjectCmdBase):
         elif manager == "deb":
             packages = sorted(set(all_packages["deb"]))
             if packages:
-                cmd_args = ["sudo", "apt", "install", "-y"] + packages
+                cmd_args = [
+                    "sudo",
+                    "--preserve-env=http_proxy",
+                    "apt-get",
+                    "install",
+                    "-y",
+                ] + packages
         elif manager == "homebrew":
             packages = sorted(set(all_packages["homebrew"]))
             if packages:
@@ -1155,7 +1161,7 @@ jobs:
                 build_opts.allow_system_packages
                 and build_opts.host_type.get_package_manager()
             ):
-                sudo_arg = "sudo "
+                sudo_arg = "sudo --preserve-env=http_proxy "
                 allow_sys_arg = " --allow-system-packages"
                 if build_opts.host_type.get_package_manager() == "deb":
                     out.write("    - name: Update system package info\n")