WIP: Refactor CMake build system to more modular

cmake/osdetection.cmake

@@ -0,0 +1,36 @@
+if(CMAKE_SYSTEM_NAME MATCHES "Linux")
+    set(LINUX TRUE)
+endif(CMAKE_SYSTEM_NAME MATCHES "Linux")
+
+if(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+    set(FREEBSD true)
+endif(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+
+option(FAT_RUNTIME "Build a library that supports multiple microarchitectures" OFF)
+message("Checking Fat Runtime Requirements...")
+if (FAT_RUNTIME AND NOT LINUX)
+    message(FATAL_ERROR "Fat runtime is only supported on Linux OS")
+endif()
+    
+if (FAT_RUNTIME AND LINUX)
+    if (NOT (ARCH_IA32 OR ARCH_X86_64 OR ARCH_AARCH64))
+        message(FATAL_ERROR "Fat runtime is only supported on Intel and Aarch64 architectures")
+    else()
+        message(STATUS "Building Fat runtime for multiple microarchitectures")
+	message(STATUS "generator is ${CMAKE_GENERATOR}")
+        if (NOT (CMAKE_GENERATOR MATCHES "Unix Makefiles" OR
+            (CMAKE_VERSION VERSION_GREATER "3.0" AND CMAKE_GENERATOR MATCHES "Ninja")))
+	    message (FATAL_ERROR "Building the fat runtime requires the Unix Makefiles generator, or Ninja with CMake v3.0 or higher")
+        else()
+            include (${CMAKE_MODULE_PATH}/attrib.cmake)
+            if (NOT HAS_C_ATTR_IFUNC)
+                message(FATAL_ERROR "Compiler does not support ifunc attribute, cannot build fat runtime")
+            endif()
+        endif()
+    endif()
+    if (NOT RELEASE_BUILD)
+        message(FATAL_ERROR "Fat runtime is only built on Release builds")
+    endif()
+endif ()
+
+