Add symbol visibility macros to abi-breaking.h.cmake (#110898)

Annotating these symbols will fix missing symbols errors for Bugpoint
when when the default symbol visibility is set to hidden for LLVM.

This is part of the work to enable LLVM_BUILD_LLVM_DYLIB and plugins on
window.

Co-authored-by: Tom Stellard <[email protected]>

Author: fsfod

llvm/include/llvm/Config/abi-breaking.h.cmake

@@ -12,6 +12,8 @@
 #ifndef LLVM_ABI_BREAKING_CHECKS_H
 #define LLVM_ABI_BREAKING_CHECKS_H
 
+#include "llvm/Support/Compiler.h"
+
 /* Define to enable checks that alter the LLVM C++ ABI */
 #cmakedefine01 LLVM_ENABLE_ABI_BREAKING_CHECKS
 
@@ -43,12 +45,12 @@
 #endif
 namespace llvm {
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
-extern int EnableABIBreakingChecks;
+LLVM_ABI extern int EnableABIBreakingChecks;
 LLVM_HIDDEN_VISIBILITY
 __attribute__((weak)) int *VerifyEnableABIBreakingChecks =
     &EnableABIBreakingChecks;
 #else
-extern int DisableABIBreakingChecks;
+LLVM_ABI extern int DisableABIBreakingChecks;
 LLVM_HIDDEN_VISIBILITY
 __attribute__((weak)) int *VerifyDisableABIBreakingChecks =
     &DisableABIBreakingChecks;