community/dfc: fix incorrect sysconfdir

Previously the file /usr/etc/xdg/dfc/dfcrc would be installed which is
incorrect. Fix this by explitely setting the sysconfdir.

community/dfc/APKBUILD

@@ -2,7 +2,7 @@
 # Maintainer: Bart Ribbers <bribbers@disroot.org>
 pkgname=dfc
 pkgver=3.1.1
-pkgrel=1
+pkgrel=2
 arch="all"
 url="https://projects.gw-computing.net/projects/dfc"
 pkgdesc="Report file system space usage information with style"
@@ -15,7 +15,8 @@ options="!check" # No tests available
 build() {
 	cmake \
 		-DCMAKE_BUILD_TYPE=None \
-		-DCMAKE_INSTALL_PREFIX=/usr
+		-DCMAKE_INSTALL_PREFIX=/usr \
+		-DSYSCONFDIR=/etc
 	make
 }