logd: build liblogd and its test on host

Plus the various fixups needed for building on host.

Test: run these tests on host
Change-Id: I85e6c989068f80c5a80eaf5ad149fdad0a045c08
diff --git a/logd/LogBufferTest.cpp b/logd/LogBufferTest.cpp
index 806fd16..cc3cb76 100644
--- a/logd/LogBufferTest.cpp
+++ b/logd/LogBufferTest.cpp
@@ -36,6 +36,16 @@
 using android::base::Join;
 using android::base::StringPrintf;
 
+#ifndef __ANDROID__
+unsigned long __android_logger_get_buffer_size(log_id_t) {
+    return 1024 * 1024;
+}
+
+bool __android_logger_valid_buffer_size(unsigned long) {
+    return true;
+}
+#endif
+
 void android::prdebug(const char* fmt, ...) {
     va_list ap;
     va_start(ap, fmt);