Flang plugin doesn't raise an error with `-O0` and intrinsics

[joewallwork]

Consider the dot_with_bindings_O0 test and make the following edits:

diff --git a/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90 b/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90
index 383d7c7a..24d76f00 100644
--- a/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90
+++ b/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90
@@ -1,6 +1,5 @@
 ! REQUIRES: fortran
 ! UNSUPPORTED: ifx
-! RUN: %fc -flto -O0 -c %loadFortran %s -o /dev/stdout | %opt %loadEnzyme %enzyme -o %t.ll && %fc -flto -O0 %t.ll -o %t1 && %t1 | FileCheck %s
 ! RUN: %if flangenzyme %{ %fc -O0 %loadFortran %loadFlangEnzyme %s -o %t2 && %t2 | FileCheck %s %}
 
 ! NOTE: This test is only configured to run with the flang compiler at -O0
@@ -67,15 +66,7 @@ contains
     real, dimension(n), intent(in) :: a
     real, dimension(n), intent(in) :: b
     real, intent(in) :: c
-    integer :: i
-    ! TODO: Use the `dot_product` intrinsic.
-    !       Requires accounting for `_FortranADotProductReal4` for this to work
-    !       at -O0
-    ! dot = dot_product(a, b) + c
-    dot = c
-    do i = 1, n
-      dot = dot + a(i) * b(i)
-    end do
+    dot = dot_product(a, b) + c
   end function dot
 
 end program main

That is, only consider running with the Flang plugin and attempt to differentiate the dot_product intrinsic.

Running locally, I get the following runtime error

[0/2] Re-checking globbed directories...                                                                                                                                                                                              
[0/2] Running enzyme fortran integration tests                                                                                                                                                                                        
FAIL: Enzyme :: Fortran/ReverseMode/dot_with_bindings_O0.f90 (14 of 15)                                                                                                                                                               
******************** TEST 'Enzyme :: Fortran/ReverseMode/dot_with_bindings_O0.f90' FAILED ********************                                                                                                                        
Exit Code: 1                                                                                                                                                                                                                          
                                                                                                                                                                                                                                      
Command Output (stderr):                                                                                                                                                                                                              
--                                                                                                                                                                                                                                    
RUN: at line 3: flang -O0 -I/home/joe/tools/enzyme/build/flang/modules  -fpass-plugin=/home/joe/tools/enzyme/build/flang/Enzyme/FlangEnzyme-21.so /home/joe/tools/enzyme/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90 -o /
home/joe/tools/enzyme/build/flang/test/Fortran/ReverseMode/Output/dot_with_bindings_O0.f90.tmp2 && /home/joe/tools/enzyme/build/flang/test/Fortran/ReverseMode/Output/dot_with_bindings_O0.f90.tmp2 | FileCheck /home/joe/tools/enzyme
/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90                                                                                                                                                                             
+ flang -O0 -I/home/joe/tools/enzyme/build/flang/modules -fpass-plugin=/home/joe/tools/enzyme/build/flang/Enzyme/FlangEnzyme-21.so /home/joe/tools/enzyme/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90 -o /home/joe/tools/
enzyme/build/flang/test/Fortran/ReverseMode/Output/dot_with_bindings_O0.f90.tmp2                                                                                                                                                      
+ /home/joe/tools/enzyme/build/flang/test/Fortran/ReverseMode/Output/dot_with_bindings_O0.f90.tmp2                                                                                                                                    
+ FileCheck /home/joe/tools/enzyme/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90                                                                                                                                           
/home/joe/tools/enzyme/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90:74:10: error: CHECK: expected string not found in input
! CHECK: 20.0
         ^
<stdin>:1:1: note: scanning from here
 0.0
^
<stdin>:1:2: note: possible intended match here
 0.0
 ^

Input file: <stdin>
Check file: /home/joe/tools/enzyme/enzyme/test/Fortran/ReverseMode/dot_with_bindings_O0.f90

-dump-input=help explains the following input dump.

Input was:
<<<<<<
            1:  0.0 
check:74'0     X~~~~ error: no match found
check:74'1      ?    possible intended match
            2:  0.0 
check:74'0     ~~~~~
            3:  1.0 
check:74'0     ~~~~~
            4:  0.0 
check:74'0     ~~~~~
            5:  0.0 
check:74'0     ~~~~~
            6:  1.0 
check:74'0     ~~~~~
            .
            .
            .
>>>>>>

--

********************
********************
Failed Tests (1):
  Enzyme :: Fortran/ReverseMode/dot_with_bindings_O0.f90

i.e., the outputs are all zero. This should instead raise a compile-time error.