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/PKGBUILD

@@ -10,7 +10,7 @@
 pkgname=distcc-avahi
 _pkgname=distcc
 pkgver=3.4
-pkgrel=18
+pkgrel=19
 pkgdesc="Distributed compilation service for C, C++ and Objective-C (with Avahi/Zeroconf support)"
 arch=('x86_64' 'aarch64')
 url="https://github.com/distcc/distcc"
@@ -37,7 +37,7 @@ sha256sums=(
     'a4f1d1bb21d61d41f22e918b448cfb852a6d95b0d3b922bd82805090cb2ce41a'
     'd8aee2eb895c02a39e0f2b76fd4a5c9dce91405f1c443286ca324628eadbf3f1'
     '7ff56af2ea505bfbf65ceeb0c8f752295f73ffb1173c26a6e978840fad04f651'
-    'f7d5e02298db44f46763b28ca509e9151e8331ce8cc9a732f1b5f49923d03f47'
+    '17141d91a5c80235287d16390a588395ab8fa5fbd129679966721625e604d8f4'
 )
 
 prepare() {
@@ -79,4 +79,16 @@ package() {
     install -Dm644 ../distccd.conf    "${pkgdir}/etc/conf.d/distccd"
     install -Dm644 ../distccd.service "${pkgdir}/usr/lib/systemd/system/distccd.service"
     install -Dm644 ../distcc.tmpfiles "${pkgdir}/usr/lib/tmpfiles.d/distcc.conf"
+
+    # Compiler symlinks — mirror Arch upstream layout so makepkg's
+    # buildenv_distcc() picks /usr/lib/distcc/bin up. Without the bin/
+    # subdir the BUILDENV=(distcc ...) hook is silently a no-op.
+    local _targets=(c++ c89 c99 cc clang clang++ cpp g++ gcc
+                    "${CHOST}-g++" "${CHOST}-gcc"
+                    "${CHOST}-gcc-$(gcc -dumpversion)")
+    install -d "${pkgdir}/usr/lib/${_pkgname}/bin"
+    for _bin in "${_targets[@]}"; do
+        ln -sf "../../bin/${_pkgname}"    "${pkgdir}/usr/lib/${_pkgname}/${_bin}"
+        ln -sf "../../../bin/${_pkgname}" "${pkgdir}/usr/lib/${_pkgname}/bin/${_bin}"
+    done
 }