[gimp-help] build: on Windows also support MINGW.

[Jacob Boerema <jboerema src gnome org>]

commit 166ed6964c91b2613cd3b102212e0b70238b897f
Author: Jacob Boerema <jgboerema gmail com>
Date:   Thu Apr 1 14:08:00 2021 -0400

    build: on Windows also support MINGW.
    
    It seems that until now only CygWin was supported on Windows.
    Also test for existence of MINGW because that is now most
    often used for building on Windows.

 configure.ac             | 2 +-
 make.d/test/is_cygwin.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 25bbd977d..a00c8283a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,7 +15,7 @@ AC_INIT([GIMP-Help], [help_version])
 # Apparently this macro must be called before "AM_INIT_AUTOMAKE"
 AC_CANONICAL_BUILD
 case $build_os in
-  *cygwin*) IS_CYGWIN=yes;;
+  *cygwin*|mingw*) IS_CYGWIN=yes;;
          *) IS_CYGWIN=no;;
 esac
 # for use in Makefile.am
diff --git a/make.d/test/is_cygwin.sh b/make.d/test/is_cygwin.sh
index 84f5129e6..f158a0a84 100644
--- a/make.d/test/is_cygwin.sh
+++ b/make.d/test/is_cygwin.sh
@@ -2,7 +2,7 @@
 
 type uname >/dev/null 2>&1 || exit 1
 case `uname -s` in
-       *[Cc][Yy][Gg][Ww][Ii][Nn]*)
+       *[Cc][Yy][Gg][Ww][Ii][Nn]*|[Mm][Ii][Nn][Gg][Ww]*)
                echo 1
                ;;
        *)