patch 9.2.0410: test suite races when run with parallel make

Problem:  Running "make test" with -jN causes spurious failures because
          the old-style tests share filenames (test.ok, test.out, X*,
          viminfo) in the working directory.
Solution: Add .NOTPARALLEL to the testdir Makefile to prevent parallel
          execution of tests (Jesse Rosenstock).

closes: #20082

Co-authored-by: Gemini
Signed-off-by: Jesse Rosenstock <jmr@google.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/Makefile

@@ -2,6 +2,11 @@
 # Makefile to run all tests for Vim
 #
 
+# The old-style tests (*.in) use shared filenames in the working directory
+# (test.ok, test.out, X*, viminfo), so running them in parallel causes races
+# and spurious failures.
+.NOTPARALLEL:
+
 # Use console or GUI.
 VIMPROG = ../vim
 XXDPROG = ../xxd/xxd

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    410,
 /**/
     409,
 /**/