This patch makes the UUIDs in the XMP header optional, depending on the
setting of the environment variable GS_GENERATE_UUIDS.

If the environment variable GS_GENERATE_UUIDS is set to "0" or "no", it will
not write out the Document UUID field and also will write the Instance ID
field value as "".

Upstream does not want to do this.

See: https://bugs.ghostscript.com/show_bug.cgi?id=698208
diff -ur orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c aa/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c
--- orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c	2017-07-09 23:30:28.960479189 +0200
+++ gnu-ghostscript-9.14.0/devices/vector/gdevpdfe.c	2017-07-10 01:04:12.252478276 +0200
@@ -620,7 +620,7 @@
         return code;
 
     /* PDF/A XMP reference recommends setting UUID to empty. If not empty must be a URI */
-    if (pdev->PDFA != 0)
+    if (pdev->PDFA != 0 || (getenv("GS_GENERATE_UUIDS") && (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") == 0 || strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") == 0)))
         instance_uuid[0] = 0x00;
 
     cre_date_time_len = pdf_get_docinfo_item(pdev, "/CreationDate", cre_date_time, sizeof(cre_date_time));
@@ -720,14 +720,17 @@
             pdf_xml_tag_close(s, "rdf:Description");
             pdf_xml_newline(s);
 
-            pdf_xml_tag_open_beg(s, "rdf:Description");
-            pdf_xml_copy(s, " rdf:about=\"\"");
-            pdf_xml_attribute_name(s, "xmlns:xapMM");
-            pdf_xml_attribute_value(s, "http://ns.adobe.com/xap/1.0/mm/");
-            pdf_xml_attribute_name(s, "xapMM:DocumentID");
-            pdf_xml_attribute_value(s, document_uuid);
-            pdf_xml_tag_end_empty(s);
-            pdf_xml_newline(s);
+            if (!getenv("GS_GENERATE_UUIDS") || (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") != 0 && strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") != 0))
+            {
+                pdf_xml_tag_open_beg(s, "rdf:Description");
+                pdf_xml_copy(s, " rdf:about=\"\"");
+                pdf_xml_attribute_name(s, "xmlns:xapMM");
+                pdf_xml_attribute_value(s, "http://ns.adobe.com/xap/1.0/mm/");
+                pdf_xml_attribute_name(s, "xapMM:DocumentID");
+                pdf_xml_attribute_value(s, document_uuid);
+                pdf_xml_tag_end_empty(s);
+                pdf_xml_newline(s);
+            }
 
             pdf_xml_tag_open_beg(s, "rdf:Description");
             pdf_xml_copy(s, " rdf:about=\"\"");
<a href='/guix/log/build-aux/update-NEWS.scm?id=3634c55ce48a73a5b728f74a3e890ba3f9b43bcb&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-05-10 13:48:02 -0400'>2021-05-10</span></td><td><a href='/guix/commit/build-aux/update-NEWS.scm?id=ed2d4d52dde00bdccc1bb2c93b24ffcc72a7fcd3'>maint: update-NEWS: Sort packages prior writing to the data file.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-04-23 21:32:46 -0400'>2021-04-23</span></td><td><a href='/guix/commit/build-aux/update-NEWS.scm?id=18dc8c6f0f76b8d128638105eebad2895f9857f0'>build-aux: Relax the regexp used to match NEWS sections.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2019-05-20 11:50:21 +0200'>2019-05-20</span></td><td><a href='/guix/commit/build-aux/update-NEWS.scm?id=996ecaf64e397341dbed70198032ce828040e5ac'>maint: update-NEWS: Track "gcc-toolchain", not "gcc".</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-12-05 00:08:34 +0100'>2018-12-05</span></td><td><a href='/guix/commit/build-aux/update-NEWS.scm?id=e3c03952be99419b958e98e5934fb3b86f71165d'>maint: update-NEWS: Don't produce full package lists.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-09-02 16:43:10 +0200'>2018-09-02</span></td><td><a href='/guix/commit/build-aux/update-NEWS.scm?id=fe634eaf93ba40862acdf62d7f197c6f19f0651c'>Add (guix describe) and use it to initialize '%package-search-path'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>