Fix linux/CI build breaker.

cmake/compilerFlagsExiv2.cmake

@@ -1,8 +1,14 @@
 # These flags only applies to exiv2lib, and the applications, but not to the xmp code
 
+include(CheckCXXCompilerFlag)
+
 if (COMPILER_IS_GCC OR COMPILER_IS_CLANG) # MINGW, Linux, APPLE, CYGWIN
     if ( EXIV2_TEAM_WARNINGS_AS_ERRORS )
-        add_compile_options(-Werror -Wno-error=deprecated-declarations -Wno-error=deprecated-copy)
+        add_compile_options(-Werror -Wno-error=deprecated-declarations)
+        check_cxx_compiler_flag(-Wno-error=deprecated-copy DEPRECATED_COPY)
+        if ( DEPRECATED_COPY) 
+            add_compile_options(-Wno-error=deprecated-copy)
+        endif ()
     endif ()
 
     if ( EXIV2_TEAM_EXTRA_WARNINGS )