BCommandPipe: Fix memory leak.

CID 600866. Both the header and the source of the argv getter
clearly indicate that the caller must free the memory.

src/kits/shared/CommandPipe.cpp

@@ -362,6 +362,7 @@ BCommandPipe::operator<<(const BCommandPipe& arg)
 	for (int32 i = 0; i < argc; i++)
 		AddArg(argv[i]);
 
+	free(argv);
 	return *this;
 }