cmake: Rename macos.cmake to darwin

cmake/os-specific/darwin.cmake

@@ -0,0 +1,41 @@
+message(
+  STATUS
+    "Configuring for Darwin (Apple stationary operating systems (macOS, OS X, etc.)"
+)
+
+target_compile_definitions(
+  common
+  INTERFACE HAVE_SOCKADDR_SA_LEN
+            HAVE_GETHOSTBYNAME2
+            HAVE_UNION_SEMUN
+            HAVE_SCHED_YIELD
+            USE_ANON_MMAP
+            NDEBUG # NDEBUG used to turn off assert (assert wants to call
+            # eprintf which doesn't seem to be defined in any shared lib
+            HAVE_CONNECT_ECONNRESET_BUG
+            HAVE_TIMEGM
+            USE_SIGWAIT
+            HAVE_IP_MREQN
+)
+
+target_link_libraries(common INTERFACE resolv)
+
+message(STATUS "USE_FAST_LOCK = ${USE_FAST_LOCK}")
+if(NOT ${USE_FAST_LOCK})
+  target_compile_definitions(common INTERFACE USE_PTHREAD_MUTEX USE_SYSV_SEM)
+endif()
+
+set(CMAKE_MODULE_LINKER_FLAGS
+    "${CMAKE_MODULE_LINKER_FLAGS} -bundle -flat_namespace -undefined suppress"
+)
+set(CMAKE_SHARED_LINKER_FLAGS
+    "${CMAKE_SHARED_LINKER_FLAGS} -dynamiclib -flat_namespace -undefined suppress"
+)
+
+if(NOT DEFINED ${NO_SELECT})
+  target_compile_definitions(common INTERFACE HAVE_SELECT)
+endif()
+
+if(NOT DEFINED ${NO_KQUEUE})
+  target_compile_definitions(common INTERFACE HAVE_KQUEUE)
+endif()