cmake: Install pkgconfig file in mingw
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 888b8e0..998d733 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -417,7 +417,7 @@
 
 # ----------------------------------------------------------------------------
 # installation directories
-if (OS_WINDOWS)
+if (OS_WINDOWS AND NOT MINGW)
   set (RUNTIME_INSTALL_DIR "bin")
   set (LIBRARY_INSTALL_DIR "lib")
   set (INCLUDE_INSTALL_DIR "include")