Make sure that all globals are internal, except for "start" functions.

tests_lit/llvm2ice_tests/prune_unreachable.ll

Index: tests_lit/llvm2ice_tests/prune_unreachable.ll
diff --git a/tests_lit/llvm2ice_tests/prune_unreachable.ll b/tests_lit/llvm2ice_tests/prune_unreachable.ll
index 0c77acd1a8dfeb41332fe33505cd52bfe5f321f5..7ce93e96d964f8faedcfb0e2be0469af2bed5519 100644
--- a/tests_lit/llvm2ice_tests/prune_unreachable.ll
+++ b/tests_lit/llvm2ice_tests/prune_unreachable.ll
@@ -1,12 +1,14 @@
 ; This tests that unreachable basic blocks are pruned from the CFG, so that
 ; liveness analysis doesn't detect inconsistencies.
 
-; RUN: %p2i -i %s --filetype=obj --disassemble --args -Om1 | FileCheck %s
-; RUN: %p2i -i %s --filetype=obj --disassemble --args -O2 | FileCheck %s
+; RUN: %p2i -i %s --filetype=obj --disassemble --args -Om1 \
+; RUN:      -allow-externally-defined-symbols | FileCheck %s
+; RUN: %p2i -i %s --filetype=obj --disassemble --args -O2 \
+; RUN:      -allow-externally-defined-symbols | FileCheck %s
 
 declare void @abort()
 
-define i32 @unreachable_block() {
+define internal i32 @unreachable_block() {
 entry:
   ; ret_val has no reaching uses and so its assignment may be
   ; dead-code eliminated.