distcc-avahi: 3.4-19 — install /usr/lib/distcc/bin/ symlinks (closes #6)

Mirror Arch upstream's /usr/lib/$pkgname/bin/<compiler> -> ../../../bin/distcc
symlink farm in package(). Without it, makepkg's buildenv_distcc() check
[[ -d /usr/lib/distcc/bin ]] fails, BUILDENV=(distcc ...) is silently a
no-op, and aarch64 builds compile locally instead of distributing.

Also keeps the legacy /usr/lib/$pkgname/<compiler> -> ../../bin/distcc
flat layout that update-distcc-symlinks(1) used to produce, so distcc
hosts using the Debian-style invocation continue to work.

Drop the post_install/_warn_masq update-distcc-symlinks dance since the
symlinks now ship in the package. Add pre_upgrade hook that strips
untracked legacy symlinks from <= 3.4-18 so pacman can drop the new
tracked ones in their place without a file conflict.

Compiler set matches Arch upstream (c++ c89 c99 cc clang clang++ cpp g++
gcc, plus \$CHOST-{gcc,g++,gcc-\$(gcc -dumpversion)}).

arch/distcc-avahi/distcc-avahi.install

@@ -8,21 +8,32 @@ _fix_conf() {
     fi
 }
 
-_warn_masq() {
-    if [ ! -d /usr/lib/distcc ]; then
-        echo "==> distcc-avahi: /usr/lib/distcc/ not populated; running update-distcc-symlinks"
-        /usr/bin/update-distcc-symlinks 2>/dev/null || true
-    fi
+_clean_legacy_symlinks() {
+    # Versions <= 3.4-18 shipped no symlinks in the package and instead ran
+    # /usr/sbin/update-distcc-symlinks at .install time, leaving untracked
+    # files at /usr/lib/distcc/<compiler>. Remove those so pacman can drop
+    # the now-tracked symlinks in their place without a file conflict.
+    local d=/usr/lib/distcc
+    [ -d "$d" ] || return 0
+    local f
+    for f in "$d"/*; do
+        [ -L "$f" ] || continue
+        case "$(readlink "$f")" in
+            ../../bin/distcc) rm -f "$f" ;;
+        esac
+    done
 }
 
 post_install() {
     _fix_conf
-    _warn_masq
+}
+
+pre_upgrade() {
+    _clean_legacy_symlinks
 }
 
 post_upgrade() {
     _fix_conf
-    _warn_masq
     if systemctl is-active --quiet distccd 2>/dev/null; then
         echo "==> distcc-avahi: distccd.service is active; restart with"
         echo "    'sudo systemctl restart distccd' to pick up any conf change"