fix: skip GPS auto-detect on SenseCAP Solar (P1 Pro)

[syssi]

Problem

The GPS detection in EnvironmentSensorManager::initBasicGPS() waits only 1 second before checking Serial1.available() > 0. Cold-starting GPS modules commonly need 2–5 seconds before outputting NMEA sentences. On the SenseCAP Solar (P1 Pro) the GPS doesn't respond within that window, so gps_detected stays false, hiding all GPS CLI commands and preventing GPS time sync entirely. See #2258 for the underlying issue affecting most GPS-equipped variants.

Workaround

Sets ENV_SKIP_GPS_DETECT=1 in the SenseCAP Solar build flags, bypassing the unreliable detection check and marking the GPS as present unconditionally. This is consistent with how other affected variants are handled (LilyGo TBeam 1W, ThinkNode M1/M5, Station G2).

build_flags = ...
  -D ENV_SKIP_GPS_DETECT=1

Note

This is a stopgap until #2258 is resolved with a proper fix in initBasicGPS() (e.g. a retry loop up to 5 seconds). Once that lands, this flag becomes redundant.