Silence remaining unused-parameter warnings

Suppressing these individually would add too much clutter.

fesvr/syscall.cc

@@ -17,6 +17,10 @@ using namespace std::placeholders;
 
 #define RISCV_AT_FDCWD -100
 
+#ifdef __GNUC__
+# pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
 struct riscv_stat
 {
   target_endian<uint64_t> dev;

riscv/interactive.cc

@@ -20,6 +20,10 @@
 #include <algorithm>
 #include <math.h>
 
+#ifdef __GNUC__
+# pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
 #define MAX_CMD_STR 40 // maximum possible size of a command line
 #define BITS_PER_CHAR 8