Backport
https://github.com/colobot/colobot/commit/1561854b03500d39955c66971c9c98de1937d7e6

Check if SDL_main is in use
The main() function of colobot-app is declared as extern "C" to prevent
name mangling. This is required because on some platforms, SDL2 declares
its own main() function and defines a macro that renames the user's main
to SDL_main; in which case, name mangling may cause linking failures.

However, when building for platforms where this is not the case,
gcc15 complains that specifying linkage for main is not allowed.
> error: cannot declare ‘::main’ with a linkage
>        specification [-Wpedantic]

This commit wraps the extern block in #ifdefs that check
if the main -> SDL_main macro is in use.

Fixes sparc64 compile.
-- 
:wq Claudio

Index: colobot/patches/patch-src_app_main_cpp
===================================================================
RCS file: colobot/patches/patch-src_app_main_cpp
diff -N colobot/patches/patch-src_app_main_cpp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ colobot/patches/patch-src_app_main_cpp	16 Dec 2025 09:35:34 -0000
@@ -0,0 +1,35 @@
+Backport of commit 1561854b03500d39955c66971c9c98de1937d7e6
+
+gcc15 complains that specifying linkage for main is not allowed.
+> error: cannot declare ‘::main’ with a linkage
+>        specification [-Wpedantic]
+
+This commit wraps the extern block in #ifdefs that check
+if the main -> SDL_main macro is in use.
+
+Index: src/app/main.cpp
+--- src/app/main.cpp.orig
++++ src/app/main.cpp
+@@ -94,10 +94,14 @@ The current layout is the following:
+  - src/script - link with the CBot library
+ */
+ 
+-//! Entry point to the program
++// On *some* platforms, SDL declares a macro which renames main to SDL_main.
++// If that's the case, use "extern C" to prevent name mangling.
++#ifdef main
+ extern "C"
+ {
++#endif
+ 
++//! Entry point to the program
+ int main(int argc, char *argv[])
+ {
+     CLogger logger; // single instance of logger
+@@ -176,4 +180,6 @@ int main(int argc, char *argv[])
+     return code;
+ }
+ 
++#ifdef main
+ } // extern "C"
++#endif