[SPEC] Define arch/os portability flag for LoongArch

Similar to #158. Without this change, 500.perlbench_r will fail to
build on LoongArch.

Author: SixWeining

External/SPEC/SpecCPU2017.cmake

@@ -157,6 +157,8 @@ macro (speccpu2017_benchmark)
     elseif (ARCH STREQUAL "AArch64" AND TARGET_OS STREQUAL "Linux" AND CMAKE_SIZEOF_VOID_P EQUAL 8)
       # Linux ARM
       list(APPEND SPEC_COMMON_DEFS "-DSPEC_LINUX_AARCH64")
+    elseif (ARCH STREQUAL "LoongArch")
+      list(APPEND SPEC_COMMON_DEFS "-DSPEC_MANUAL_CONFIG")
     elseif (ARCH STREQUAL "riscv64")
       list(APPEND SPEC_COMMON_DEFS "-DSPEC_MANUAL_CONFIG")
     elseif (ARCH STREQUAL "x86" AND TARGET_OS STREQUAL "Windows")