Userland: env: Add -i / --ignore-environment arg to clear env

Author: https://github.com/bcoles
Commit: 7a512c4cc4
Pull-request: https://github.com/SerenityOS/serenity/pull/4064

Userland/env.cpp

@@ -39,6 +39,12 @@ int main(int argc, char** argv)
     const char* filename = nullptr;
 
     for (int idx = 1; idx < argc; ++idx) {
+        if (idx == 1) {
+            if (StringView { argv[idx] } == "-i" || StringView { argv[idx] } == "--ignore-environment") {
+                *environ = NULL;
+                continue;
+            }
+        }
         if (StringView { argv[idx] }.contains('=')) {
             putenv(argv[idx]);
         } else {