adns: fix Darwin properly

The post‐facto install name replacement was unpredictably running
out of space; just patch the build system to do the right thing
instead. And don’t use `.so` on Darwin, either.

pkgs/by-name/ad/adns/darwin.patch

···
+diff --git a/configure.in b/configure.in
+index b753a5bb3e..ee7d546984 100644
+--- a/configure.in
++++ b/configure.in
+@@ -134,12 +134,12 @@
+ AC_SUBST(SHLIBFILE)
+ AC_SUBST(SHLIBSONAME)
+ 
+-SHLIBFORLINK='libadns.so'
+-SHLIBSONAME='$(SHLIBFORLINK).$(MAJOR)'
+-SHLIBFILE='$(SHLIBSONAME).$(MINOR)'
++SHLIBFORLINK='libadns.dylib'
++SHLIBSONAME='libadns.$(MAJOR).dylib'
++SHLIBFILE='libadns.$(MAJOR).$(MINOR).dylib'
+ 
+ SHLIBCC='$(CC) $(CFLAGS) -fpic'
+-MKSHLIB_1='$(CC) $(LDFLAGS) -shared -Wl,-soname=$(SHLIBSONAME) -o'
++MKSHLIB_1='$(CC) $(LDFLAGS) -shared -Wl,-install_name,$(libdir)/$(SHLIBFILE) -o'
+ MKSHLIB_2=''
+ MKSHLIB_3='-lc'
+ 

pkgs/by-name/ad/adns/package.nix

···
   stdenv,
   fetchurl,
   gnum4,
+  autoreconfHook,
   gitUpdater,
 }:
 
···
     hash = "sha256-cTizeJt1Br1oP0UdT32FMHepGAO3s12G7GZ/D5zUAc0=";
   };
 
-  nativeBuildInputs = [ gnum4 ];
+  patches = lib.optionals stdenv.hostPlatform.isDarwin [ ./darwin.patch ];
+
+  nativeBuildInputs = [
+    gnum4
+    autoreconfHook
+  ];
 
   configureFlags = lib.optional stdenv.hostPlatform.isStatic "--disable-dynamic";
 
···
   # https://www.mail-archive.com/[e-mail]/msg01347.html for details.
   doCheck = false;
 
-  # darwin executables fail, but I don't want to fail the 100-500 packages depending on this lib
-  doInstallCheck = !stdenv.hostPlatform.isDarwin;
-
-  preConfigure = lib.optionalString stdenv.hostPlatform.isDarwin "sed -i -e 's|-Wl,-soname=$(SHLIBSONAME)||' configure";
-
-  postInstall =
-    let
-      suffix = lib.versions.majorMinor version;
-    in
-    lib.optionalString stdenv.hostPlatform.isDarwin ''
-      install_name_tool -id $out/lib/libadns.so.${suffix} $out/lib/libadns.so.${suffix}
-    '';
+  doInstallCheck = true;
 
   installCheckPhase = ''
     runHook preInstallCheck