sqlite: refactor how CFLAGS are passed to the configure script

Change the way the SQLITE_CONF_ENV variable is constructed in
preparation of passing other CFLAGS to the configure script.

Signed-off-by: Sven Neumann <s.neumann@raumfeld.com>
Reviewed-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/sqlite/sqlite.mk

@@ -13,9 +13,11 @@ ifneq ($(BR2_LARGEFILE),y)
 # the sqlite configure script fails to define SQLITE_DISABLE_LFS when
 # --disable-largefile is passed, breaking the build. Work around it by
 # simply adding it to CFLAGS for configure instead
-SQLITE_CONF_ENV = CFLAGS="$(TARGET_CFLAGS) -DSQLITE_DISABLE_LFS"
+SQLITE_CFLAGS += -DSQLITE_DISABLE_LFS
 endif
 
+SQLITE_CONF_ENV = CFLAGS="$(TARGET_CFLAGS) $(SQLITE_CFLAGS)"
+
 SQLITE_CONF_OPT = \
 	--enable-threadsafe \
 	--localstatedir=/var