Building with LTO=1 is broken

[opsound]

Building with make clean; make -j8 TARGET=CF2 LTO=1 yields the following warnings/errors:

src/drivers/interface/ws2812.h:5:6: warning: type of 'ws2812Send' does not match original declaration [-Wlto-type-mismatch]
 void ws2812Send(uint8_t (*color)[3], uint16_t len);
      ^
src/drivers/src/ws2812_cf2.c:172:6: note: type mismatch in parameter 2
 void ws2812Send(uint8_t (*color)[3], int len)
      ^
src/drivers/src/ws2812_cf2.c:172:6: note: type 'int' should match type 'uint16_t'
/Users/stro/.local/share/gcc-arm-none-eabi/arm-none-eabi/include/sys/_stdint.h:36:20: note: the incompatible type is defined here
 typedef __uint16_t uint16_t ;
                    ^
src/drivers/src/ws2812_cf2.c:172:6: note: 'ws2812Send' was previously declared here
 void ws2812Send(uint8_t (*color)[3], int len)
      ^
src/drivers/src/ws2812_cf2.c:172:6: note: code may be misoptimized unless -fno-strict-aliasing is used
/var/folders/z_/vk4r28_515s8wx74gvlq84_w0000gn/T//ccivFwGD.ltrans15.ltrans.o: In function `PendSV_Handler':
<artificial>:(.text+0x466): undefined reference to `vTaskSwitchContext'
collect2: error: ld returned 1 exit status
make: *** [cf2.elf] Error 1
rm version.c

These changes get it to build cleanly:

diff --git a/src/drivers/src/ws2812_cf2.c b/src/drivers/src/ws2812_cf2.c
index 6d5d521..c946d2c 100644
--- a/src/drivers/src/ws2812_cf2.c
+++ b/src/drivers/src/ws2812_cf2.c
@@ -169,7 +169,7 @@ static int current_led = 0;
 static int total_led = 0;
 static uint8_t (*color_led)[3] = NULL;

-void ws2812Send(uint8_t (*color)[3], int len)
+void ws2812Send(uint8_t (*color)[3], uint16_t len)
 {
     int i;
        if(len<1) return;
diff --git a/src/lib/FreeRTOS/tasks.c b/src/lib/FreeRTOS/tasks.c
index 11ca0e9..6adf9db 100644
--- a/src/lib/FreeRTOS/tasks.c
+++ b/src/lib/FreeRTOS/tasks.c
@@ -2200,7 +2200,7 @@ BaseType_t xSwitchRequired = pdFALSE;
 #endif /* configUSE_APPLICATION_TASK_TAG */
 /*-----------------------------------------------------------*/

-void vTaskSwitchContext( void )
+void __attribute__((used)) vTaskSwitchContext( void )^M
 {
        if( uxSchedulerSuspended != ( UBaseType_t ) pdFALSE )
        {