Added CMake configuration for Fugaku with LLVM 19

and also applied the following fix to xtensor:
xtensor-stack/xtensor#2833
to resolve LLVM 19.

Author: amanotk

cmake/fugaku-llvm19-cross.cmake

@@ -0,0 +1,18 @@
+#
+# LLVM-19.1.4 cross compiler on Fugaku Login Node
+#
+# Seting up the environment with the following commands is needed:
+#
+# $ . /vol0004/apps/oss/llvm-v19.1.4/init.sh
+#
+set(CMAKE_SYSTEM_NAME Fugaku)
+set(CMAKE_SYSTEM_PROCESSOR aarch64)
+set(MPI_THREAD_MULTIPLE OFF CACHE BOOL "MPI thread multiple" FORCE)
+set(LLVM_LIB "/vol0004/apps/oss/llvm-v19.1.4/login_node/lib")
+
+set(CMAKE_CXX_COMPILER "mpiclang++" CACHE FILEPATH "C++ compiler")
+set(CMAKE_CXX_FLAGS "-Wno-unused-command-line-argument \
+    -mtune=a64fx -mcpu=a64fx -march=armv8.2-a+sve -msve-vector-bits=512 \
+    -fopenmp -O3"
+    CACHE STRING "C++ compiler flags")
+set(CMAKE_EXE_LINKER_FLAGS "-L${LLVM_LIB}" CACHE STRING "Linker flags")