Make this pass for CYGWIN.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44354 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CFrontend/extern-weak.c b/test/CFrontend/extern-weak.c
index b131f33..2a8569c 100644
--- a/test/CFrontend/extern-weak.c
+++ b/test/CFrontend/extern-weak.c
@@ -1,7 +1,8 @@
 // RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | grep extern_weak
 // RUN: %llvmgcc -O3 -S -o - -emit-llvm %s | llvm-as | llc
 
-#if !defined(__linux__) && !defined(__FreeBSD__) && !defined(__OpenBSD__)
+#if !defined(__linux__) && !defined(__FreeBSD__) && \
+    !defined(__OpenBSD__) && !defined(__CYGWIN__)
 void foo() __attribute__((weak_import));
 #else
 void foo() __attribute__((weak));