[gimp/gimp-2-10] libgimpwidgets: fix automake syntaxe.

[Jehan <jehanp src gnome org>]

commit 555efb528dc68022792739cabe7d90210ebf7caa
Author: Jehan <jehan girinstud io>
Date:   Tue Oct 11 00:29:57 2022 +0200

    libgimpwidgets: fix automake syntaxe.
    
    Automake doesn't accept the "if else" syntax. Instead, we must add a new if/else
    inside the first else block.
    
    While I'm at it, I also add a G_GNUC_INTERNAL to the internal function
    _gimp_pick_button_win32_pick(), though I don't think it's absolutely necessary
    (yet explicit is better).
    
    (cherry picked from commit 8ac51782143f55c2dbf85856567f82bee707f308)

 libgimpwidgets/Makefile.am            | 6 +++++-
 libgimpwidgets/gimppickbutton-win32.h | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/libgimpwidgets/Makefile.am b/libgimpwidgets/Makefile.am
index 82d25edb36..9b4dbf5bad 100644
--- a/libgimpwidgets/Makefile.am
+++ b/libgimpwidgets/Makefile.am
@@ -316,7 +316,9 @@ EXTRA_DIST = \
 if PLATFORM_OSX_QUARTZ
 libgimpwidgets_sources += gimppickbutton-quartz.c gimppickbutton-quartz.h
 AM_CPPFLAGS += "-xobjective-c"
-else if PLATFORM_WIN32
+else
+
+if PLATFORM_WIN32
 libgimpwidgets_sources += gimppickbutton-win32.c gimppickbutton-win32.h
 else
 libgimpwidgets_sources += \
@@ -328,6 +330,8 @@ libgimpwidgets_sources += \
        gimppickbutton-xdg.h
 endif
 
+endif
+
 
 #
 # rules to generate built sources
diff --git a/libgimpwidgets/gimppickbutton-win32.h b/libgimpwidgets/gimppickbutton-win32.h
index f28de815a6..eaeaa776ec 100644
--- a/libgimpwidgets/gimppickbutton-win32.h
+++ b/libgimpwidgets/gimppickbutton-win32.h
@@ -18,6 +18,6 @@
 #ifndef __GIMP_PICK_BUTTON_WIN32_H__
 #define __GIMP_PICK_BUTTON_WIN32_H__
 
-void _gimp_pick_button_win32_pick (GimpPickButton *button);
+G_GNUC_INTERNAL void _gimp_pick_button_win32_pick (GimpPickButton *button);
 
 #endif /* __GIMP_PICK_BUTTON_WIN32_H__ */