Wrap system calls in TEMP_FAILURE_RETRY.

fs_prepare_dir() is used heavily during Zygote init, and can easily
run into EINTR.

Bug: 7151474
Change-Id: I7aac43a43483d55db47ca20456fff68ce51bbc46
diff --git a/include/cutils/fs.h b/include/cutils/fs.h
index 04c8839..fd5296b 100644
--- a/include/cutils/fs.h
+++ b/include/cutils/fs.h
@@ -19,6 +19,21 @@
 
 #include <sys/types.h>
 
+/*
+ * TEMP_FAILURE_RETRY is defined by some, but not all, versions of
+ * <unistd.h>. (Alas, it is not as standard as we'd hoped!) So, if it's
+ * not already defined, then define it here.
+ */
+#ifndef TEMP_FAILURE_RETRY
+/* Used to retry syscalls that can return EINTR. */
+#define TEMP_FAILURE_RETRY(exp) ({         \
+    typeof (exp) _rc;                      \
+    do {                                   \
+        _rc = (exp);                       \
+    } while (_rc == -1 && errno == EINTR); \
+    _rc; })
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif