[lld][ELF] Mark empty NOLOAD output sections SHT_NOBITS instead of SHT_PROGBITS

[schultetwin1]

Summary

This fixes PR# 45336.
Output sections described in a linker script as NOLOAD with no input sections would be marked as SHT_PROGBITS.

[MaskRay]

Fix title. Improve test

[MaskRay]

Thanks! I've adjusted the test a bit.

[schultetwin1]

Thank you! It looks Harbormaster was unable to apply the patch, but that other "buildables" before this one are failing for the same reason. So I'm going to assume this isn't a problem with this diff.

lld/ELF/ScriptParser.cpp

bool ScriptParser::readSectionDirective(OutputSection *cmd, StringRef tok1, StringRef tok2) {
   if (tok1 != "(")
     return false;
   if (tok2 != "NOLOAD" && tok2 != "COPY" && tok2 != "INFO" && tok2 != "OVERLAY")
     return false;
 
   expect("(");
   if (consume("NOLOAD")) {
     cmd->noload = true;
+    cmd->type = SHT_NOBITS;
   } else {
     skip(); // This is "COPY", "INFO" or "OVERLAY".
     cmd->nonAlloc = true;
   }
   expect(")");
   return true;
 }
 

lld/test/ELF/linkerscript/noload.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
 # RUN: echo "SECTIONS { \
 # RUN:        .data_noload_a (NOLOAD) : { *(.data_noload_a) } \
 # RUN:        .data_noload_b (0x10000) (NOLOAD) : { *(.data_noload_b) } \
+# RUN:        .no_input_sec_noload (NOLOAD) : { . += 1; } \
 # RUN:        .text (0x20000) : { *(.text) } };" > %t.script
 # RUN: ld.lld -o %t --script %t.script %t.o
 # RUN: llvm-readelf -S -l %t | FileCheck %s
 
-# CHECK:      Name           Type   Address          Off               Size
-# CHECK:      .data_noload_a NOBITS 0000000000000000 [[OFF:[0-9a-f]+]] 001000
-# CHECK-NEXT: .data_noload_b NOBITS 0000000000010000 [[OFF]]           001000
+# CHECK:      Name                 Type   Address          Off               Size
+# CHECK:      .data_noload_a       NOBITS 0000000000000000 [[OFF:[0-9a-f]+]] 001000
+# CHECK-NEXT: .data_noload_b       NOBITS 0000000000010000 [[OFF]]           001000
+# CHECK-NEXT: .no_input_sec_noload NOBITS 0000000000011000 [[OFF]]           000001
 
 # CHECK:      Type Offset   VirtAddr           PhysAddr
 # CHECK-NEXT: LOAD 0x001000 0x0000000000020000 0x0000000000020000
 
 .section .text,"ax",@progbits
   nop
 
 .section .data_noload_a,"aw",@progbits
 .zero 4096
 
 .section .data_noload_b,"aw",@progbits
 .zero 4096