Fix compile on windows with clang (#1480)

Co-authored-by: Jordan Bayles <bayles.jordan@gmail.com>
diff --git a/src/lib_json/CMakeLists.txt b/src/lib_json/CMakeLists.txt
index 3cf66eb..ce8100b 100644
--- a/src/lib_json/CMakeLists.txt
+++ b/src/lib_json/CMakeLists.txt
@@ -144,7 +144,7 @@
 
     # avoid name clashes on windows as the shared import lib is also named jsoncpp.lib
     if(NOT DEFINED STATIC_SUFFIX AND BUILD_SHARED_LIBS)
-        if (MSVC)
+        if (WIN32)
             set(STATIC_SUFFIX "_static")
         else()
             set(STATIC_SUFFIX "")