LibJS: Remove the seal/unseal of Bytecode::Block again

This partially reverts c6ce7c9326f8e745e29ede503ea011f10c76fc5f.
The munmap part of that change was good, but we can't seal the blocks
since that breaks NewString and other ops that have String members.

Userland/Libraries/LibJS/Bytecode/Block.cpp

@@ -28,7 +28,6 @@ Block::Block()
 
 Block::~Block()
 {
-    unseal();
     Bytecode::InstructionStreamIterator it(instruction_stream());
     while (!it.at_end()) {
         auto& to_destroy = (*it);
@@ -39,20 +38,12 @@ Block::~Block()
     munmap(m_buffer, m_buffer_capacity);
 }
 
-void Block::seal() const
+void Block::seal()
 {
-    if (mprotect(m_buffer, m_buffer_capacity, PROT_READ) < 0) {
-        perror("ByteCode::Block::seal: mprotect");
-        VERIFY_NOT_REACHED();
-    }
-}
-
-void Block::unseal()
-{
-    if (mprotect(m_buffer, m_buffer_capacity, PROT_READ | PROT_WRITE) < 0) {
-        perror("ByteCode::Block::unseal: mprotect");
-        VERIFY_NOT_REACHED();
-    }
+    // FIXME: mprotect the instruction stream as PROT_READ
+    // This is currently not possible because instructions can have destructors (that clean up strings)
+    // Instructions should instead be destructor-less and refer to strings in a string table on the Bytecode::Block.
+    // It also doesn't work because instructions that have String members use RefPtr internally which must be in writable memory.
 }
 
 void Block::dump() const

Userland/Libraries/LibJS/Bytecode/Block.h

@@ -42,8 +42,7 @@ public:
     static NonnullOwnPtr<Block> create();
     ~Block();
 
-    void seal() const;
-    void unseal();
+    void seal();
 
     void dump() const;
     ReadonlyBytes instruction_stream() const { return ReadonlyBytes { m_buffer, m_buffer_size }; }