kernel: Properly initialize the shebang read buffer with zeros

Before this patch, a shebang line that was too long could have left the buffer without a null terminator, allowing some other stack contents to pass into the m_interpreter_cmdline.

kernel/src/binfmt/Script.cpp

@@ -16,6 +16,8 @@ Result<bool> ScriptLoader::sniff()
 Result<u64> ScriptLoader::load(AddressSpace* space)
 {
     u8 buf[256];
+    memset(buf, 0, sizeof(buf));
+    
     usize nread = TRY(m_inode->read(buf, 2, 255));
     if (!nread) return err(ENOEXEC);
     for (usize i = 0; i < nread; i++)