Issue #27490: Do not build pgen when cross-compiling

The dependendency on the $(PGEN) variable must only be
set when not cross-compiling. When cross-compiling,
$(PGEN) will not be used, so no need to build it.

Patch by Thomas Perl.
diff --git a/Misc/ACKS b/Misc/ACKS
index 2b32fb8..a4a4cdc 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1120,6 +1120,7 @@
 Bo Peng
 Santiago Peresón
 George Peristerakis
+Thomas Perl
 Mathieu Perreault
 Mark Perrego
 Trevor Perrin
diff --git a/Misc/NEWS b/Misc/NEWS
index 3ac2ed3..799e1f0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -145,6 +145,9 @@
 Build
 -----
 
+- Issue #27490: Do not build pgen when cross-compiling.  Patch by Thomas
+  Perl.
+
 - Issue #26662: Set PYTHON_FOR_GEN in configure as the Python program to be
   used for file generation during the build.