Default linker scripts are stored in:
XC32 Compiler: "C:\Program Files (x86)\Microchip\xc32\v1.10\pic32-libs\proc\"
To use a customised version simply copy it into your projects folder. Do NOT add it to your project in MPLAB X, only copy it into the project directory (if you add it you also have to add the primary elf32pic32mx.* but by not adding it the file will automatically get used by virtue of the include search path priorities).