libbinder: on host

The usecase is unit testing things which implement binder interfaces.

Bug: 124524556
Test: TH runs all relevant unit tests
Change-Id: I8caba1290da6d0354a7736a26d1dad7b6ab852e6
diff --git a/libs/binder/Static.cpp b/libs/binder/Static.cpp
index a6fd8c4..bd40536 100644
--- a/libs/binder/Static.cpp
+++ b/libs/binder/Static.cpp
@@ -54,7 +54,9 @@
 protected:
     virtual status_t writeLines(const struct iovec& vec, size_t N)
     {
-        writev(mFD, &vec, N);
+        ssize_t ret = writev(mFD, &vec, N);
+        if (ret == -1) return -errno;
+        if (static_cast<size_t>(ret) != N) return UNKNOWN_ERROR;
         return NO_ERROR;
     }