community/gnu-libiconv: enable extra encodings

CP437 in particular which is unfortunately missing in the default set of
enable encodings.

community/gnu-libiconv/APKBUILD

 # Maintainer: Natanael Copa <ncopa@alpinelinux.org>
 pkgname=gnu-libiconv
 pkgver=1.15
-pkgrel=2
+pkgrel=3
 pkgdesc="GNU charset conversion library for libc which doesn't implement it"
 url="https://www.gnu.org/software/libiconv"
 arch="all"
@@ -19,7 +19,10 @@ build() {
 		--prefix=/usr \
 		--mandir=/usr/share/man \
 		--disable-nls \
-		--disable-static
+		--disable-static \
+		--enable-extra-encodings
+	# since users of this package use this package to work around missing features in musls iconv,
+	# enable extra encodings (like the CP437) to be closer to glibcs iconv.
 
 	# work around rpath issue
 	sed -i 's|^hardcode_libdir_flag_spec=.*|hardcode_libdir_flag_spec=""|g' libtool