Replace CONFIG_NOWAIT env var with -w option

And document the -w option

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16325)
diff --git a/Configure b/Configure
index 2264e09..b00b91a 100755
--- a/Configure
+++ b/Configure
@@ -63,6 +63,8 @@
 #               (Default: PREFIX/ssl)
 # --banner=".." Output specified text instead of default completion banner
 #
+# -w            Don't wait after showing a Configure warning
+#
 # --cross-compile-prefix Add specified prefix to binutils components.
 #
 # --api         One of 0.9.8, 1.0.0, 1.0.1, 1.0.2, 1.1.0, 1.1.1, or 3.0
@@ -898,7 +900,7 @@
                 {
                 $guess_opts{verbose} = 1;
                 }
-        elsif (/^-w$/)          # From older 'config'
+        elsif (/^-w$/)
                 {
                 $guess_opts{nowait} = 1;
                 }