The slirp patch was included in this QEMU release

CXX_DEPENDS is now added for all host components otherwise we get
errors like the following

  Package qemu-img is missing dependencies for the following libraries:
  libuClibc++.so.0
  Package qemu-nbd is missing dependencies for the following libraries:
  libuClibc++.so.0

--disable-bluez was removed from configure args because upstream
deprecated bluetooth subsystem since qemu v3.1 and remove the code in
commit 1d4ffe8dc77c ("Remove the core bluetooth code")

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

Add fallback zero value definition for MAP_SYNC etc. even when building
for CONFIG_LINUX.

Fixes openwrt/packages#11067

Reported-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>