[llvm] [Cygwin] Define LLVM_ABI for Cygwin (PR #143222)

[Tomohiro Kashiwada via llvm-commits]

https://github.com/kikairoya created https://github.com/llvm/llvm-project/pull/143222

592243c1cb3ea53b34033132a87b0d14af9d1079 should be also applied to LLVM_ABI.

>From 40b636c7a306c3e3f04d01599ae06e65ba20f307 Mon Sep 17 00:00:00 2001
From: kikairoya <kikairoya at gmail.com>
Date: Sat, 7 Jun 2025 10:11:43 +0900
Subject: [PATCH] [Cygwin] Define LLVM_ABI for Cygwin

592243c1cb3ea53b34033132a87b0d14af9d1079 should be also applied to LLVM_ABI.
---
 llvm/include/llvm/Support/Compiler.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/include/llvm/Support/Compiler.h b/llvm/include/llvm/Support/Compiler.h
index b4382057654ba..904ab88a5a51f 100644
--- a/llvm/include/llvm/Support/Compiler.h
+++ b/llvm/include/llvm/Support/Compiler.h
@@ -209,7 +209,7 @@
 #define LLVM_ABI_FRIEND LLVM_ABI
 #define LLVM_ABI_EXPORT __declspec(dllexport)
 #elif defined(__ELF__) || defined(__MINGW32__) || defined(_AIX) ||             \
-    defined(__MVS__)
+    defined(__MVS__) || defined(__CYGWIN__)
 #define LLVM_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_ABI_FRIEND
 #define LLVM_TEMPLATE_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT