shared: Fix compilation errors with musl
shared: Fix compilation errors with musl

C       src/shared/hci.o
src/shared/hci.c: In function 'send_command':
src/shared/hci.c:139:2: error: implicit declaration of function
    'writev' [-Werror=implicit-function-declaration]
  if (writev(fd, iov, iovcnt) < 0)
  ^
cc1: all warnings being treated as errors
Makefile:5422: recipe for target 'src/shared/hci.o' failed
make[1]: *** [src/shared/hci.o] Error 1

pstglia/external-bluetooth-bluez,ComputeCycles/bluez,ComputeCycles/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,ComputeCycles/bluez,mapfau/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,silent-snowman/bluez,mapfau/bluez,silent-snowman/bluez,mapfau/bluez,ComputeCycles/bluez,pkarasev3/bluez,pkarasev3/bluez,pkarasev3/bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez