[DebugInfo][test] Adjust line table unit length to account for contents

Previously, if a debug line Prologue was created via
createBasicPrologue, its TotalLength field did not account for any
contents in the table itself. This change fixes this issue.

Reviewed by: probinson

Differential Revision: https://reviews.llvm.org/D73772

llvm/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp

@@ -549,9 +549,8 @@ TEST_F(DebugLineBasicFixture, ErrorForUnitLengthTooLarge) {
   LT.addStandardOpcode(DW_LNS_const_add_pc, {});
   LT.addExtendedOpcode(1, DW_LNE_end_sequence, {});
   DWARFDebugLine::Prologue Prologue = LT.createBasicPrologue();
-  // Set the total length to 1 higher than the actual length. The program body
-  // has size 5.
-  Prologue.TotalLength += 6;
+  // Set the total length to 1 higher than the actual length.
+  ++Prologue.TotalLength;
   LT.setPrologue(Prologue);
 
   generate();

llvm/unittests/DebugInfo/DWARF/DwarfGenerator.cpp

@@ -175,6 +175,7 @@ DWARFDebugLine::Prologue dwarfgen::LineTable::createBasicPrologue() const {
     P.TotalLength += 4;
     P.FormParams.Format = DWARF64;
   }
+  P.TotalLength += Contents.size();
   P.FormParams.Version = Version;
   P.MinInstLength = 1;
   P.MaxOpsPerInst = 1;