gdbstub: abstract target specific details from gdb_put_packet_binary

We unfortunately handle the checking of packet acknowledgement
differently for user and softmmu modes. Abstract the user mode stuff
behind gdb_got_immediate_ack with a stub for softmmu.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230302190846.2593720-14-alex.bennee@linaro.org>
Message-Id: <20230303025805.625589-14-richard.henderson@linaro.org>

gdbstub/user.c

@@ -54,6 +54,25 @@ int gdb_get_char(void)
     return ch;
 }
 
+bool gdb_got_immediate_ack(void)
+{
+    int i;
+
+    i = gdb_get_char();
+    if (i < 0) {
+        /* no response, continue anyway */
+        return true;
+    }
+
+    if (i == '+') {
+        /* received correctly, continue */
+        return true;
+    }
+
+    /* anything else, including '-' then try again */
+    return false;
+}
+
 void gdb_put_buffer(const uint8_t *buf, int len)
 {
     int ret;