Add pld linux build target

packaging/Dockerfile

@@ -1,5 +1,9 @@
 #
 # To build for arm, see https://www.docker.com/blog/getting-started-with-docker-for-arm-on-linux/
+#
+# Build targets supported:
+# docker build --build-arg=TARGET=pld packaging
+# docker build --build-arg=TARGET=debian packaging
 
 ARG VERSION=v1.0pre7
 ARG TARGET=debian
@@ -12,6 +16,9 @@ RUN git clone --depth=1 -b $VERSION https://github.com/ruediger/VobSub2SRT /sour
 FROM debian:buster AS build-debian
 RUN apt update && apt install -y libtiff5-dev libtesseract-dev tesseract-ocr-eng build-essential cmake pkg-config
 
+FROM registry.gitlab.com/pld-linux/pld AS build-pld
+RUN poldek -u cmake gzip libtiff-devel make tesseract-devel
+
 FROM build-$TARGET AS build
 WORKDIR /build
 COPY --from=source /source .