Fix build for Gentoo

src/osd_rmw.cpp

@@ -4,8 +4,26 @@
 #include <stdexcept>
 #include <string.h>
 #include <assert.h>
-#include <jerasure/reed_sol.h>
+extern "C" {
-#include <jerasure.h>
+#if defined __has_include
+
+#  if __has_include (<jerasure.h>)
+#    include <jerasure.h>
+#  endif
+
+// In Gentoo hasn't jerasure directory with header files.
+#  if __has_include (<reed_sol.h>)
+#    include <reed_sol.h>
+#  elif __has_include (<jerasure/reed_sol.h>)
+#    include <jerasure/reed_sol.h>
+#  endif
+
+#else
+// default path to headers in Debian
+#  include <jerasure/reed_sol.h>
+#  include <jerasure.h>
+#endif
+}
 #include <map>
 #include "allocator.h"
 #include "xor.h"