Allow conditional lit tests in Subzero, based on build flags.

tests_lit/reader_tests/unnamed.ll

 ; Tests that we name unnamed global addresses.
 
-; Check that the ICE converter handles renaming correctly.
-; RUN: %l2i --no-local-syms -i %s --insts | FileCheck %s
+; Check that Subzero's bitcode reader handles renaming correctly.
+; RUN: %p2i --no-local-syms -i %s --insts | %ifp FileCheck %s
+; RUN: %l2i --no-local-syms -i %s --insts | %ifl FileCheck %s
 
 ; RUN: %l2i --no-local-syms -i %s --insts --args --exit-success \
 ; RUN:      -default-function-prefix=h -default-global-prefix=g \
-; RUN:      | FileCheck --check-prefix=BAD %s
-
-; Check that Subzero's bitcode reader handles renaming correctly.
-; RUN: %p2i --no-local-syms -i %s --insts | FileCheck %s
+; RUN:      | %ifl FileCheck --check-prefix=BAD %s
 
 ; RUN: %p2i --no-local-syms -i %s --insts --args --exit-success \
 ; RUN:      -default-function-prefix=h -default-global-prefix=g \
-; RUN:      | FileCheck --check-prefix=BAD %s
+; RUN:      | %ifp FileCheck --check-prefix=BAD %s
 
 ; TODO(kschimpf) Check global variable declarations, once generated.
 
 @0 = internal global [4 x i8] zeroinitializer, align 4
 @1 = internal constant [10 x i8] c"Some stuff", align 1
 @g = internal global [4 x i8] zeroinitializer, align 4
 
 define i32 @2(i32 %v) {
   ret i32 %v
 }
@@ skipping 26 matching lines @@
   ret void
 }
 
 ; CHECK-NEXT: define void @h5() {
 ; CHECK-NEXT: __0:
 ; CHECK-NEXT:   ret void
 ; CHECK-NEXT: }
 
 ; BAD: Warning : Default global prefix 'g' potentially conflicts with name 'g'.
 ; BAD: Warning : Default function prefix 'h' potentially conflicts with name 'h5'.