Split Makefile and add build flags

This commit add support to build flags
Currently is included: support for pthreads, LTO builds and Debug
builds.

Emscripten docker image is updated from 2.0.20 to 3.1.3.

Split the Makefile into several files to build/m4.

Changed from Autotools to Meson where its possible, to reduce the
number of patches.

Removed libass.cpp, this can be implemented in SubtitleOctopus.cpp

Add zip task to make bundles

.gitignore

@@ -32,3 +32,4 @@ node_modules/
 build/lib
 src/SubOctpInterface.cpp
 src/SubOctpInterface.js
+build/__pycache__/

Dockerfile

@@ -1,4 +1,4 @@
-FROM emscripten/emsdk:2.0.20
+FROM docker.io/emscripten/emsdk:3.1.3
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
         build-essential \
@@ -10,6 +10,10 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         itstool \
         pkg-config \
         python3 \
+        python3-pip \
+        python3-setuptools \
+        python3-wheel \
+        ninja-build \
         python3-ply \
         gettext \
         autopoint \
@@ -18,7 +22,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         m4 \
         gperf \
         licensecheck \
-    && rm -rf /var/lib/apt/lists/*
+    && rm -rf /var/lib/apt/lists/* \
+    && pip3 install meson 
 
 WORKDIR /code
 CMD ["make"]