Meta: Make the manpage website build work with manpage subsection

For now, we create simple but complete indices and actually generate the
HTML for the manpages in subsections. For these purposes, switch to
using "find" as a file finding tool everywhere, instead of the very
limited globs from before.

Meta/build-manpages-website.sh

@@ -14,6 +14,9 @@ if [[ -e output ]]; then
     exit 1
 fi
 
+# Use case-insensitive sorting, which will lead to more intuitive index pages.
+SORT="sort -f"
+
 # Prepare output directories
 for d in "${MAN_DIR}"*/; do
     dir_name=$(basename "$d")
@@ -26,23 +29,26 @@ done
 # If you're here because your local results are different from the website:
 # Check that your pandoc version matches the pandoc-version specified in manpages.yaml.
 
-for md_file in "${MAN_DIR}"*/*.md; do
+for md_file in $(find "${MAN_DIR}" -iname '*.md' | ${SORT}); do
     relative_path="$(realpath --relative-to="${MAN_DIR}" "${md_file}")"
     section="${relative_path%%/*}"
     section_number="${section#man}"
     filename="${relative_path#*/}"
     name="${filename%.md}"
+    output_file="output/${section}/${name}.html"
+
+    mkdir -p "$(dirname "${output_file}")"
     pandoc -f gfm -t html5 -s \
         -B Meta/Websites/man.serenityos.org/banner-preamble.inc \
         --lua-filter=Meta/convert-markdown-links.lua \
         --metadata title="${name}(${section_number}) - SerenityOS man pages" \
-        -o "output/${section}/${name}.html" \
+        -o "${output_file}" \
         "${md_file}"
 done
 
 # Generate man page listings through pandoc
-for d in output/*/; do
-    section=$(basename "$d")
+for section_directory in output/*/; do
+    section=$(basename "${section_directory}")
     section_number="${section#man}"
     case "${section_number}" in
         1) section_title="User Programs";;
@@ -50,18 +56,19 @@ for d in output/*/; do
         3) section_title="Library Functions";;
         4) section_title="Special Files";;
         5) section_title="File Formats";;
-        6) section_title="Games";; # TODO: Populate this section
+        6) section_title="Games";;
         7) section_title="Miscellanea";;
         8) section_title="Sysadmin Tools";;
         *) section_title="SerenityOS man pages"; echo "WARNING: Unrecognized section ${section_number}?!";;
     esac
+    output="output/${section}/index.html"
     pandoc -f gfm -t html5 -s \
         -B Meta/Websites/man.serenityos.org/banner-preamble.inc \
         --metadata title="Section ${section_number} - ${section_title}" \
-        -o "output/${section}/index.html" \
+        -o "${output}" \
         <(
-            for f in "$d"/*; do
-                filename=$(basename "$f")
+            for f in $(find "${section_directory}" -iname '*.html' | ${SORT}); do
+                filename=$(realpath --relative-to="${section_directory}" "$f")
                 name="${filename%.html}"
                 if [[ "$filename" == "index.html" ]]; then
                     continue