[build] Fix the output path of the iOS ccache scripts

iOS ccache wrapper scripts should be in the top level
of the CMake build tree, so fix the output path in the
configure_file().

platform/ios/ccache.cmake

@@ -3,8 +3,8 @@ if(CCACHE_PROGRAM)
     # Set up wrapper scripts
     set(C_LAUNCHER "${CCACHE_PROGRAM}")
     set(CXX_LAUNCHER "${CCACHE_PROGRAM}")
-    configure_file(${PROJECT_SOURCE_DIR}/platform/ios/ccache-c.in ccache-c)
-    configure_file(${PROJECT_SOURCE_DIR}/platform/ios/ccache-cxx.in ccache-cxx)
+    configure_file(${PROJECT_SOURCE_DIR}/platform/ios/ccache-c.in ${CMAKE_BINARY_DIR}/ccache-c)
+    configure_file(${PROJECT_SOURCE_DIR}/platform/ios/ccache-cxx.in ${CMAKE_BINARY_DIR}/ccache-cxx)
     execute_process(
         COMMAND
             chmod