Unable to copy file to /var/<myfolder> from .pkg installer

We have .pkg installer for our appliation in which we are copying some files to "/var/<myfolder>". This .pkg installer works fine till 10.10 but in 10.11 while copying file to "/var/<myfolder> prompts error and failed to copy files. It shows the below error in Install.log

Jul  3 17:11:50 MacBook-Pro installer[431]: Set authorization level to root for session\
Jul  3 17:11:50 MacBook-Pro installer[431]: Administrator authorization granted.\
Jul  3 17:11:50 MacBook-Pro installer[431]: Will use PK session\
Jul  3 17:11:50 MacBook-Pro installer[431]: Using authorization level of root for IFPKInstallElement\
Jul  3 17:11:50 MacBook-Pro installer[431]: Package generated system content warning: Error Domain=IFInstallErrorDomain Code=-5000 "This package is incompatible with this version of OS X and may fail to install." UserInfo=0x7ff750cce3d0 \{NSLocalizedRecoveryOptions=(\
    "Cancel Installation",\
    "Install Anyway"\
  ), NSLocalizedRecoverySuggestion=Installing this package may damage your system, and the installation may fail. To stop the program and the installation, click \'93Cancel Installation\'94., IFSystemPathsKey=(\
    "var/gct/gdme2dn.xml",\
    "var/gct/gdmuimg.bin",\
    "var/gct/gdme2dn",\
    "System/Library/LaunchDaemons/com.gct.dts.gdme2dn.plist",\
    "var/gct/libWiMAXSDK.dylib"\
  ), NSLocalizedDescription=This package is incompatible with this version of OS X and may fail to install.\}\
Jul  3 17:11:50 MacBook-Pro installer[431]: Starting installation:\

- Able to copy all these file maually in "/var/gct" but not from .pkg installer

- There is no permission issue on "/var/gct" becuase manually it copying successfully.

- Please help why installer throws the warning and ubable to copy these files?

Thanks in advance.