Fixing endif guard in gpsd.h-tail to match guard levels

GARMIN_TEXT was mixed up with NMEA_ENABLED
Another pass at build_option_testing script

expanded which flags where being tested
dropped it back to minimal format
added an always on (minimal)
remove the .scons-options-cache before every run to prevent
cross-contamination
remove running the regression tests
added -j9 build option to speed things up
add .gcno to .gitignore