Minimal changes to build fastboot as a library.

Bug: http://b/77809061
Test: builds
Change-Id: I0c388334d643a0a2abf0c03a29f336dc3af2f83f
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index 005ba5a..3d5a261 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -34,8 +34,7 @@
 
 #include <string>
 
-#include "transport.h"
-
+class Transport;
 struct sparse_file;
 
 /* protocol.c - fastboot protocol */
@@ -97,4 +96,9 @@
 /* Current product */
 extern char cur_product[FB_RESPONSE_SZ + 1];
 
+class FastBoot {
+  public:
+    int Main(int argc, char* argv[]);
+};
+
 #endif