kconfig: qconf: use a variable to pass packages to pkg-config

The variable, PKG, is defined at the beginning of this script.

Signed-off-by: Masahiro Yamada <[e-mail]>

scripts/kconfig/qconf-cfg.sh

···
 fi
 
 if pkg-config --exists $PKG; then
-	echo cflags=\"-std=c++11 -fPIC $(pkg-config --cflags Qt5Core Qt5Gui Qt5Widgets)\"
+	echo cflags=\"-std=c++11 -fPIC $(pkg-config --cflags $PKG)\"
 	echo libs=\"$(pkg-config --libs $PKG)\"
 	echo moc=\"$(pkg-config --variable=host_bins Qt5Core)/moc\"
 	exit 0