[libFuzzer][MSVC] Make attribute-use compatible with MSVC

Summary:
Replace attributes with macros that use equivalent declspecs
for MSVC.

Reviewers: vitalybuka

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D56512

llvm-svn: 351456
diff --git a/compiler-rt/lib/fuzzer/FuzzerMain.cpp b/compiler-rt/lib/fuzzer/FuzzerMain.cpp
index f2c8e9c..f66c057 100644
--- a/compiler-rt/lib/fuzzer/FuzzerMain.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerMain.cpp
@@ -16,6 +16,6 @@
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
 }  // extern "C"
 
-__attribute__((visibility("default"))) int main(int argc, char **argv) {
+ATTRIBUTE_INTERFACE int main(int argc, char **argv) {
   return fuzzer::FuzzerDriver(&argc, &argv, LLVMFuzzerTestOneInput);
 }