libgcrypt: revision for libgpg-error

use opt_prefix in the config file

Formula/libgcrypt.rb

@@ -4,6 +4,7 @@ class Libgcrypt < Formula
   url "https://gnupg.org/ftp/gcrypt/libgcrypt/libgcrypt-1.7.2.tar.bz2"
   mirror "https://www.mirrorservice.org/sites/ftp.gnupg.org/gcrypt/libgcrypt/libgcrypt-1.7.2.tar.bz2"
   sha256 "3d35df906d6eab354504c05d749a9b021944cb29ff5f65c8ef9c3dd5f7b6689f"
+  revision 1
 
   bottle do
     cellar :any
@@ -48,6 +49,9 @@ class Libgcrypt < Formula
                                 buildpath/"tests/.libs/random"
     system "make", "check"
     system "make", "install"
+
+    # avoid triggering mandatory rebuilds of software that hard-codes this path
+    inreplace bin/"libgcrypt-config", prefix, opt_prefix
   end
 
   test do