Address review comments

- Use `CheckFailed` instead of `report_fatal_error` in verifier
- Add tests for verifier

Author: kovdan01

llvm/lib/IR/Verifier.cpp

@@ -1754,7 +1754,7 @@ void Verifier::visitModuleFlags() {
   }
 
   if ((PAuthABIPlatform == uint64_t(-1)) != (PAuthABIVersion == uint64_t(-1)))
-    report_fatal_error(
+    CheckFailed(
         "either both or no 'aarch64-elf-pauthabi-platform' and "
         "'aarch64-elf-pauthabi-version' module flags must be present");
 

llvm/test/CodeGen/AArch64/note-gnu-property-elf-pauthabi.ll

@@ -33,7 +33,7 @@
 
 ;--- err1.ll
 
-; RUN: not --crash llc -mtriple=aarch64-linux err1.ll 2>&1 -o - | \
+; RUN: not llc -mtriple=aarch64-linux err1.ll 2>&1 -o - | \
 ; RUN:   FileCheck %s --check-prefix=ERR
 
 !llvm.module.flags = !{!0}
@@ -42,7 +42,7 @@
 
 ;--- err2.ll
 
-; RUN: not --crash llc -mtriple=aarch64-linux err2.ll 2>&1 -o - | \
+; RUN: not llc -mtriple=aarch64-linux err2.ll 2>&1 -o - | \
 ; RUN:   FileCheck %s --check-prefix=ERR
 
 !llvm.module.flags = !{!0}

llvm/test/Verifier/module-flags-note-gnu-property-elf-pauthabi.ll

@@ -0,0 +1,19 @@
+; RUN: rm -rf %t && split-file %s %t && cd %t
+
+; CHECK: either both or no 'aarch64-elf-pauthabi-platform' and 'aarch64-elf-pauthabi-version' module flags must be present
+
+;--- err1.ll
+
+; RUN: not llvm-as err1.ll -o /dev/null 2>&1 | FileCheck %s
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"aarch64-elf-pauthabi-platform", i32 2}
+
+;--- err2.ll
+
+; RUN: not llvm-as err2.ll -o /dev/null 2>&1 | FileCheck %s
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"aarch64-elf-pauthabi-version", i32 31}