17.09 release-notes: New breaking change: cc-wrapper exports more env vars

nixos/doc/manual/release-notes/rl-1709.xml

@@ -142,6 +142,18 @@ rmdir /var/lib/ipfs/.ipfs
       being dead and not building with openssl 1.1.
     </para>
   </listitem>
+  <listitem>
+    <para>
+      <literal>cc-wrapper</literal>'s setup-hook now exports a number of
+      environment variables corresponding to binutils binaries,
+      (e.g. <envar>LD</envar>, <envar>STRIP</envar>, <envar>RANLIB</envar>,
+      etc). This is done to prevent packages' build systems guessing, which is
+      harder to predict, especially when cross-compiling. However, some packages
+      have broken due to this—their build systems either not supporting, or
+      claiming to support without adequate testing, taking such environment
+      variables as parameters.
+    </para>
+  </listitem>
 </itemizedlist>
 
 <para>Other notable improvements:</para>