Add compilation flag for USB features

This allows to disable HID/OTG features on Linux to build without
libusb.

app/meson.build

@@ -74,7 +74,7 @@ if v4l2_support
     src += [ 'src/v4l2_sink.c' ]
 endif
 
-usb_support = host_machine.system() == 'linux'
+usb_support = get_option('usb') and host_machine.system() == 'linux'
 if usb_support
     src += [
         'src/usb/aoa_hid.c',

app/src/cli.c

@@ -1357,8 +1357,8 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                 opts->keyboard_input_mode = SC_KEYBOARD_INPUT_MODE_HID;
                 break;
 #else
-                LOGE("HID over AOA (-K/--hid-keyboard) is not supported on "
-                     "this platform. It is only available on Linux.");
+                LOGE("HID over AOA (-K/--hid-keyboard) is disabled (or "
+                     "unsupported on this platform).");
                 return false;
 #endif
             case OPT_MAX_FPS:
@@ -1376,8 +1376,8 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                 opts->mouse_input_mode = SC_MOUSE_INPUT_MODE_HID;
                 break;
 #else
-                LOGE("HID over AOA (-M/--hid-mouse) is not supported on this"
-                     "platform. It is only available on Linux.");
+                LOGE("HID over AOA (-M/--hid-mouse) is disabled (or "
+                     "unsupported on this platform).");
                 return false;
 #endif
             case OPT_LOCK_VIDEO_ORIENTATION:
@@ -1540,8 +1540,8 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                 opts->otg = true;
                 break;
 #else
-                LOGE("OTG mode (--otg) is not supported on this platform. It "
-                     "is only available on Linux.");
+                LOGE("OTG mode (--otg) is disabled (or unsupported on this "
+                     "platform).");
                 return false;
 #endif
             case OPT_V4L2_SINK:

meson_options.txt

@@ -5,3 +5,4 @@ option('portable', type: 'boolean', value: false, description: 'Use scrcpy-serve
 option('server_debugger', type: 'boolean', value: false, description: 'Run a server debugger and wait for a client to be attached')
 option('server_debugger_method', type: 'combo', choices: ['old', 'new'], value: 'new', description: 'Select the debugger method (Android < 9: "old", Android >= 9: "new")')
 option('v4l2', type: 'boolean', value: true, description: 'Enable V4L2 feature when supported')
+option('usb', type: 'boolean', value: true, description: 'Enable HID/OTG features when supported')