Merge pull request #69 from JohanMabille/arm_support

Do not require long double lib on OSX arm64

Author: JohanMabille

CMakeLists.txt

@@ -65,7 +65,7 @@ else()
     set(REQUIRE_DOUBLE_LIB "")
 endif()
 
-if(FFTW_USE_LONG_DOUBLE AND NOT MSVC)
+if(FFTW_USE_LONG_DOUBLE AND NOT MSVC AND NOT (APPLE AND CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64"))
     add_definitions(-DXTENSOR_FFTW_USE_LONG_DOUBLE)
     set(REQUIRE_LONG_DOUBLE_LIB "LONGDOUBLE_LIB")
 else()