Support building and running on macOS

Makefile

@@ -34,6 +34,7 @@ CFLAGS := -iquote $(OUT) -iquote src -iquote $(OUT)board-generic/ \
 		-Wold-style-definition $(call cc-option,$(CC),-Wtype-limits,) \
     -ffunction-sections -fdata-sections -fno-delete-null-pointer-checks
 CFLAGS += -flto=auto -fwhole-program -fno-use-linker-plugin -ggdb3
+CFLAGS += $(EXTRA_CFLAGS)
 
 ifeq ($(CONFIG_WANT_OPTIMIZE_SIZE), y)
 CFLAGS += -Os

klippy/chelper/compiler.h

@@ -11,7 +11,11 @@
 #ifndef __always_inline
 #define __always_inline inline __attribute__((always_inline))
 #endif
+#if !defined(clang)
 #define __visible __attribute__((externally_visible))
+#else
+#define __visible __attribute__((visibility("default")))
+#endif
 #define __noreturn __attribute__((noreturn))
 
 #define PACKED __attribute__((packed))

klippy/chelper/serialqueue.c

@@ -12,7 +12,9 @@
 // clock times, prioritizes commands, and handles retransmissions.  A
 // background thread is launched to do this work and minimize latency.
 
+#ifndef __APPLE__
 #include <linux/can.h> // // struct can_frame
+#endif
 #include <math.h> // fabs
 #include <pthread.h> // pthread_mutex_lock
 #include <stddef.h> // offsetof
@@ -300,6 +302,7 @@ static void
 input_event(struct serialqueue *sq, double eventtime)
 {
     if (sq->serial_fd_type == SQT_CAN) {
+#ifndef __APPLE__
         struct can_frame cf;
         int ret = read(sq->serial_fd, &cf, sizeof(cf));
         if (ret <= 0) {
@@ -311,6 +314,9 @@ input_event(struct serialqueue *sq, double eventtime)
             return;
         memcpy(&sq->input_buf[sq->input_pos], cf.data, cf.can_dlc);
         sq->input_pos += cf.can_dlc;
+#else
+        exit(1);
+#endif
     } else {
         int ret = read(sq->serial_fd, &sq->input_buf[sq->input_pos]
                        , sizeof(sq->input_buf) - sq->input_pos);
@@ -366,6 +372,7 @@ do_write(struct serialqueue *sq, void *buf, int buflen)
             report_errno("write", ret);
         return;
     }
+#ifndef __APPLE__
     // Write to CAN fd
     struct can_frame cf;
     while (buflen) {
@@ -389,6 +396,9 @@ do_write(struct serialqueue *sq, void *buf, int buflen)
         buf += size;
         buflen -= size;
     }
+#else
+    exit(1);
+#endif
 }
 
 // Callback timer for when a retransmit should be done

scripts/check-gcc.sh

@@ -1,6 +1,11 @@
 #!/bin/sh
 # This script checks for a broken Ubuntu 18.04 arm-none-eabi-gcc compile
 
+if [ ! -f /etc/issue ] ; then
+    # doesn't exist on mac
+    exit 0
+fi
+
 f1="$1"
 f2="$2"