mingw: Building on Fedora 22 works as well.

mingw/Dockerfile

-FROM fedora:21
+FROM fedora:22
 MAINTAINER opus@xiph.org
 
 # Linux build.
-RUN yum update -y
-RUN yum install -y git gcc make wget
-RUN yum install -y autoconf automake libtool
+RUN dnf update -y
+RUN dnf install -y git gcc make wget xz
+RUN dnf install -y autoconf automake libtool
 
 # mingw cross build.
-RUN yum install -y mingw32-gcc zip
+RUN dnf install -y mingw32-gcc zip
 
-RUN yum clean all
+RUN dnf clean all
 
 RUN git clone https://git.xiph.org/opusfile.git
 
@@ -17,3 +17,4 @@ WORKDIR opusfile
 RUN git pull
 RUN make -C mingw
 RUN ./autogen.sh && ./configure --host=i686-w64-mingw32 --prefix=${PWD}/mingw PKG_CONFIG_PATH=${PWD}/mingw/lib/pkgconfig && make && make check && make install
+RUN make -C mingw package

mingw/Makefile

@@ -88,7 +88,7 @@ ssl_BUILD: $(ssl_DIR)
 # CROSS_COMPILE="i686-w64-mingw32-" ./Configure mingw no-asm no-shared --prefix=$PWD/mingw && make depend && make -j8 && make install
 
 # Package the binaries.
-DIST=opusfile-0.7rc-f22docker-win32
+DIST := opusfile-0.7rc-f22docker-win32
 package: $(DIST).zip
 
 $(DIST).zip: $(DIST)