Add STATUS message showing Imath_DIR (#993)

A status message is reported when Imath is installed from an external
repo. This adds a similar message confirming the location of Imath
when specified via Imath_DIR.

Signed-off-by: Cary Phillips <cary@ilm.com>

cmake/OpenEXRSetup.cmake

@@ -278,4 +278,6 @@ if(NOT TARGET Imath::Imath AND NOT Imath_FOUND)
     # hrm, cmake makes Imath lowercase for the properties (to imath)
     add_subdirectory(${imath_SOURCE_DIR} ${imath_BINARY_DIR})
   endif()
+else()
+  message(STATUS "Using Imath from ${Imath_DIR}")
 endif()