Respect Env var for kvm device in qemu2.

Bug: 32731012
Change-Id: Ic282da91d760741ee0acc3e039201355876fa1f1
Signed-off-by: Tao Wu <lepton@google.com>
(cherry picked from commit beac64c94ca55de8c521efd393c06be9147153e9)
diff --git a/kvm-all.c b/kvm-all.c
index 0c07d3f..d6f25e3 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1462,7 +1462,11 @@
     QTAILQ_INIT(&s->kvm_sw_breakpoints);
 #endif
     s->vmfd = -1;
-    s->fd = qemu_open("/dev/kvm", O_RDWR);
+    const char* kvm_device = getenv("ANDROID_EMULATOR_KVM_DEVICE");
+    if (NULL == kvm_device) {
+        kvm_device = "/dev/kvm";
+    }
+    s->fd = qemu_open(kvm_device, O_RDWR);
     if (s->fd == -1) {
         fprintf(stderr, "Could not access KVM kernel module: %m\n");
         ret = -errno;