utils/gpsd: Set manbuild=no for build (disable building help/html documentation)

This removes unnecessary dependancy on xmlto which can be problematic on macOS build environment.

Signed-off-by: David Thornley <david.thornley@touchstargroup.com>

utils/gpsd/Makefile

@@ -102,6 +102,7 @@ SCONS_OPTIONS += \
 	python=no \
 	implicit_link=no \
 	chrpath=no \
+	manbuild=no \
 	target="$(TARGET_CROSS:-=)"
 
 define Build/InstallDev