Add librubberband and its dependencies

Closes #19

scripts.d/50-rubberband.sh

@@ -0,0 +1,60 @@
+#!/bin/bash
+
+# https://breakfastquay.com/rubberband/
+RUBBERBAND_SRC="https://breakfastquay.com/files/releases/rubberband-1.9.0.tar.bz2"
+
+ffbuild_enabled() {
+    [[ $VARIANT == gpl* ]] || return -1
+    return 0
+}
+
+ffbuild_dockerstage() {
+    to_df "ADD $SELF /stage.sh"
+    to_df "RUN run_stage"
+}
+
+ffbuild_dockerbuild() {
+    mkdir rubberband
+    cd rubberband
+
+    wget "$RUBBERBAND_SRC" -O rubberband.tar.gz || return -1
+    tar xaf rubberband.tar.gz || return -1
+    rm rubberband.tar.gz
+    cd rubberband* || return -1
+
+    local myconf=(
+        --prefix="$FFBUILD_PREFIX"
+        --disable-shared
+        --enable-static
+        --disable-ladspa
+        --disable-vamp
+        --disable-programs
+    )
+
+    if [[ $TARGET == win* ]]; then
+        myconf+=(
+            --host="$FFBUILD_TOOLCHAIN"
+        )
+    else
+        echo "Unknown target"
+        return -1
+    fi
+
+    ./configure "${myconf[@]}" || return -1
+    make -j$(nproc) || return -1
+    make install || return -1
+
+    # Fix static linking
+    echo "Requires.private: fftw3 samplerate" >> "$FFBUILD_PREFIX"/lib/pkgconfig/rubberband.pc
+
+    cd ../..
+    rm -rf rubberband
+}
+
+ffbuild_configure() {
+    echo --enable-librubberband
+}
+
+ffbuild_unconfigure() {
+    echo --disable-librubberband
+}