[Test] Fix undef var in catch-undef-behavior.c

[thopre]

Summary

Commit 9e52c43090f8cd980167bbd2719878ae36bcf6b5 removed the directive
defining LINE_1600 but left a string substitution to that variable in a
CHECK-NOT directive. This will make that CHECK-NOT directive always fail
to match, no matter the string.

This commit follows the pattern done in
9e52c43090f8cd980167bbd2719878ae36bcf6b5 of simplifying the CHECK-NOT to
only look for the function name and the opening parenthesis, thereby not
requiring the LINE_1600 variable.

[rnk]

lgtm

clang/test/CodeGen/catch-undef-behavior.c

signed char fp16_char_overflow(__fp16 *p) {
   // CHECK-TRAP:      call void @llvm.ubsantrap(i8 5) [[NR_NUW]]
   // CHECK-TRAP-NEXT: unreachable
 #line 1500
   return *p;
 }
 
 // CHECK-COMMON-LABEL: @float_float_overflow
 float float_float_overflow(double f) {
-  // CHECK-UBSAN-NOT: call {{.*}} @__ubsan_handle_float_cast_overflow(i8* bitcast ({{.*}} @[[LINE_1600]] to i8*),
+  // CHECK-UBSAN-NOT: call {{.*}} @__ubsan_handle_float_cast_overflow(
   // CHECK-TRAP-NOT:  call {{.*}} @llvm.ubsantrap(i8 19) [[NR_NUW]]
   // CHECK-COMMON: }
   return f;
 }
 
 // CHECK-COMMON-LABEL:   @int_divide_overflow
 // CHECK-OVERFLOW-LABEL: @int_divide_overflow
 int int_divide_overflow(int a, int b) {