[gimp] app: revert `#pragma once` to macro guards in meson build.

[Jehan <jehanp src gnome org>]

commit fdb46684f8dae669e8d6a3c781bf14d08a675ae3
Author: Jehan <jehan girinstud io>
Date:   Thu Sep 19 13:21:39 2019 +0200

    app: revert `#pragma once` to macro guards in meson build.
    
    Some change which happened with the meson port. From my research, this
    `#pragma once` is not standard, though it is apparently implemented in
    most common compilers.
    Also apparently it is based on heuristic, hence it might happen that
    file identity fails. Though unsure how often it would happen, if ever, I
    don't find this very acceptable (and probably makes for hard-to-debug
    bugs).
    
    So let's revert to basic macro guards, stupid and no heuristic, which
    don't ever fail and are very easy to read.

 app/git-version.h.in | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/app/git-version.h.in b/app/git-version.h.in
index 2adb4479f6..2cc800c6e5 100644
--- a/app/git-version.h.in
+++ b/app/git-version.h.in
@@ -1,5 +1,8 @@
-#pragma once
+#ifndef __GIT_VERSION_H__
+#define __GIT_VERSION_H__
 
 #define GIMP_GIT_VERSION          "@GIMP_GIT_VERSION@"
 #define GIMP_GIT_VERSION_ABBREV   "@GIMP_GIT_VERSION_ABBREV@"
 #define GIMP_GIT_LAST_COMMIT_YEAR "@GIMP_GIT_LAST_COMMIT_YEAR@"
+
+#endif /* __GIT_VERSION_H__ */