cmake: add DOWNLOAD_MSCG option

cmake/Modules/FindMSCG.cmake

@@ -0,0 +1,22 @@
+# - Find mscg
+# Find the native MSCG headers and libraries.
+#
+#  MSCG_INCLUDE_DIRS - where to find mscg.h, etc.
+#  MSCG_LIBRARIES    - List of libraries when using mscg.
+#  MSCG_FOUND        - True if mscg found.
+#
+
+find_path(MSCG_INCLUDE_DIR mscg.h PATH_SUFFIXES mscg)
+
+find_library(MSCG_LIBRARY NAMES mscg)
+
+set(MSCG_LIBRARIES ${MSCG_LIBRARY})
+set(MSCG_INCLUDE_DIRS ${MSCG_INCLUDE_DIR})
+
+include(FindPackageHandleStandardArgs)
+# handle the QUIETLY and REQUIRED arguments and set MSCG_FOUND to TRUE
+# if all listed variables are TRUE
+
+find_package_handle_standard_args(MSCG DEFAULT_MSG MSCG_LIBRARY MSCG_INCLUDE_DIR)
+
+mark_as_advanced(MSCG_INCLUDE_DIR MSCG_LIBRARY )