The current libgps.a logic doesn't pass down pkg-config output from
dbus and such which breaks building when compiling:

gcc -o libgps_dbus.o -c -D_GNU_SOURCE -Wextra -Wall -Wno-uninitialized \
	-Wno-missing-field-initializers -Wcast-align -Wmissing-declarations \
	-Wmissing-prototypes -Wstrict-prototypes -Wpointer-arith -Wreturn-type \
	-O2 libgps_dbus.c
libgps_dbus.c:26:23: fatal error: dbus/dbus.h: No such file or directory
compilation terminated.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Simon Dawson <spdawson@gmail.com>
---
 SConstruct | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/SConstruct b/SConstruct
index e5d1f54..a56fa9b 100644
--- a/SConstruct
+++ b/SConstruct
@@ -886,7 +886,9 @@ gpsdlibs = ["-lgpsd"] + usblibs + bluezlibs + gpslibs + caplibs
 #          linking
 # The final executable will build but not be portable.
 
-env.StaticLibrary(target = 'libgps.a', source = libgps_sources)
+env.StaticLibrary(target='libgps.a',
+                  source=libgps_sources,
+                  parse_flags=dbus_libs + rtlibs)
 
 # Source groups