Add actions for building and testing (#8)

* Add a Github action for building and testing

On Windows, -- -//third_party/... doesn't seem to work, so add all test directories manually. Also run the tests_*. We run only fastbuild tests here, since the opt tests will be run in the release workflow.

Also fix a number of compilation and test issues found along the way.

fastcdc/fastcdc.h

@@ -17,6 +17,8 @@
 #ifndef FASTCDC_FASTCDC_H_
 #define FASTCDC_FASTCDC_H_
 
+#include <string.h>
+
 #include <algorithm>
 #include <cassert>
 #include <cstdio>