[gimp/gimp-2-10] add msys support

[Jehan <jehanp src gnome org>]

commit 0a06779fee413c00dfba1fdc302aacd8dcadb0d0
Author: Marco Spiess <marco spiess andrena de>
Date:   Thu May 27 17:10:19 2021 +0200

    add msys support
    
    (cherry picked from commit 512fc2469422bb651515fb56a250439a1cc5c4ad)

 configure.ac | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 5a7e7d28ac..64cf2c4880 100644
--- a/configure.ac
+++ b/configure.ac
@@ -331,7 +331,7 @@ AM_CONDITIONAL(PLATFORM_LINUX, test "$platform_linux" = "yes")
 
 AC_MSG_CHECKING([if compiling for Win32])
 case "$host_os" in
-  mingw* | cygwin*)
+  msys* | mingw* | cygwin*)
     platform_win32=yes
     ;;
   *)
@@ -346,7 +346,7 @@ os_win32=no
 if test "x$platform_win32" != xno; then
   AC_MSG_CHECKING([if this is native Win32])
   case "$host_os" in
-    mingw*)
+    msys* | mingw*)
       os_win32=yes
       case "$host_cpu" in
         x86_64)