docker/base: take the configuration as a parameter

Rather than unconditionally run the container with the build script we
should take it as a parameter. We remove the ENTRYPOINT as a way to
ease debugging these changes.

docker/base/Dockerfile

@@ -32,5 +32,3 @@ RUN gem install asciidoctor-diagram
 
 COPY build.sh /opt/nerdcruft/
 RUN chmod a+rx /opt/nerdcruft/build.sh
-
-ENTRYPOINT /opt/nerdcruft/build.sh

docker/base/build.sh

@@ -2,9 +2,14 @@
 
 die() { echo "$*" 1>&2 ; exit 1; }
 
-buildroot="/build/"
+usage() { die "$0 [mingw]<release|debug>/<gcc|clang>" ; }
+
+buildroot="/work/"
+
+config=$1
+[ ! -z "${config}" ] || die "Empty config"
+echo "Building in '${config}'"
 
-config="release/gcc"
 configroot="${buildroot}/build/${config}/"
 
 mkdir -p "${buildroot}/" || die "Could not create buildroot"