Add Nix flake (#1)

build.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+
+USER_DIR=$(readlink -f "$1")
+WORKDIR=$(mktemp -d -p "$USER_DIR")
+
+cd "$WORKDIR" || exit 1
+
+SHELL="/bin/sh"
+
+# Build PDFs from LaTeX. Do the build twice to sort out any bookmarks.
+# For some reason, using $0 instead of `sh` makes Hadolint warn about the single-quotes not expanding expressions
+# shellcheck disable=SC2016
+find "$USER_DIR" -type f -name '*.tex' -exec "$SHELL" -c '
+  output=$(dirname "$@")/$(basename "$@" .tex).pdf
+  echo "$@ - $output"
+  HOME=$(pwd) SOURCE_DATE_EPOCH=1622905527 pdflatex "$@" || exit 1
+  HOME=$(pwd) SOURCE_DATE_EPOCH=1622905527 pdflatex "$@" || exit 1
+  mv "$(basename "$output")" "$output" || exit 1
+' -- {} \; || exit 1
+
+cd "$USER_DIR" || exit 1
+rm -r "$WORKDIR"
+