tools/bit: Avoid leak in error condition

In the unlikely event of fread() failing, we want to avoid leaking
our buffer or the file handle.

Test: Treehugger
Change-Id: I1866d00c74ad38af4559d747fee696a60464c9f0

tools/bit/util.cpp

@@ -241,6 +241,8 @@ read_file(const string& filename)
 
     char* buf = (char*)malloc(size);
     if ((size_t) size != fread(buf, 1, size, file)) {
+        free(buf);
+        fclose(file);
         return string();
     }