[ELF][x86] Always create .got.plt

glibc's -static-pie implementation expect that _GLOBAL_OFFSET_TABLE_
is at the beginning of .got.plt, as it uses the address of _DYNAMIC
which is stored at _GLOBAL_OFFSET_TABLE_[0].

In this patch, we always create .got.plt for x86-64 and i386.

elf/mold.h

@@ -489,6 +489,7 @@ class GotPltSection : public Chunk<E> {
     this->shdr.sh_type = SHT_PROGBITS;
     this->shdr.sh_flags = SHF_ALLOC | SHF_WRITE;
     this->shdr.sh_addralign = E::word_size;
+    this->shdr.sh_size = E::word_size * 3;
   }
 
   void copy_buf(Context<E> &ctx) override;

elf/output-chunks.cc

@@ -1161,10 +1161,8 @@ template <typename E>
 void PltSection<E>::add_symbol(Context<E> &ctx, Symbol<E> *sym) {
   assert(!sym->has_plt(ctx));
 
-  if (this->shdr.sh_size == 0) {
+  if (this->shdr.sh_size == 0)
     this->shdr.sh_size = ctx.plt_hdr_size;
-    ctx.gotplt->shdr.sh_size = E::word_size * 3;
-  }
 
   sym->set_plt_idx(ctx, symbols.size());
   this->shdr.sh_size += ctx.plt_size;

elf/passes.cc

@@ -1391,7 +1391,10 @@ void fix_synthetic_symbols(Context<E> &ctx) {
   start(ctx._DYNAMIC, ctx.dynamic);
 
   // _GLOBAL_OFFSET_TABLE_
-  start(ctx._GLOBAL_OFFSET_TABLE_, ctx.got);
+  if constexpr (std::is_same_v<E, X86_64> || std::is_same_v<E, I386>)
+    start(ctx._GLOBAL_OFFSET_TABLE_, ctx.gotplt);
+  else
+    start(ctx._GLOBAL_OFFSET_TABLE_, ctx.got);
 
   // __GNU_EH_FRAME_HDR
   start(ctx.__GNU_EH_FRAME_HDR, ctx.eh_frame_hdr);