FIx error when building with oneAPI release compiler (#497)

Author: muhammad-tanvir-1211

benchmark/portblas/CMakeLists.txt

@@ -26,6 +26,15 @@ if(BLAS_VERIFY_BENCHMARK)
   find_package(SystemBLAS REQUIRED)
 endif()
 
+# update CXX_FLAGS to avoid error when building benchmarks
+# in case of icpx compiler: 
+# explicit comparison with NaN in fast floating point mode [-Werror,-Wtautological-constant-compare]
+# https://github.com/dealii/dealii/issues/14693
+string(FIND ${CMAKE_CXX_COMPILER} "icpx" found_icpx)
+if(${found_icpx} GREATER -1)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error=tautological-constant-compare")
+endif()
+
 set(sources
   # Level 1 blas
   blas1/axpy.cpp