Add missing includes.

Change-Id: Ibf549266a19a67eb9158d341a69dddfb654be669
diff --git a/libc/bionic/getcwd.cpp b/libc/bionic/getcwd.cpp
index 47c807f..a8bbcf3 100644
--- a/libc/bionic/getcwd.cpp
+++ b/libc/bionic/getcwd.cpp
@@ -26,8 +26,10 @@
  * SUCH DAMAGE.
  */
 
-#include <unistd.h>
 #include <errno.h>
+#include <malloc.h>
+#include <string.h>
+#include <unistd.h>
 
 extern "C" int __getcwd(char* buf, size_t size);