Merge #3782

3782: Fixed library dependencies for the Haiku operating system r=def- a=panos

<!-- What is the motivation for the changes of this pull request -->

The TARGET_OS variable wasn't set to "haiku", which causes issues. There's still other things left to fix.

## Checklist

- [ ] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [x] Considered possible null pointers and out of bounds array indexing
- [x] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Panagiotis Vasilopoulos <hello@alwayslivid.com>

CMakeLists.txt

@@ -60,6 +60,8 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
   set(TARGET_OS "linux")
 elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
   set(TARGET_OS "mac")
+elseif(CMAKE_SYSTEM_NAME STREQUAL "Haiku")
+  set(TARGET_OS "haiku")
 endif()
 
 include(CheckCCompilerFlag)
@@ -210,12 +212,6 @@ if(NOT MSVC AND NOT HAIKU)
   add_c_compiler_flag_if_supported(OUR_FLAGS_OWN -Wthread-safety)
   # TODO: Enable for C++ code except gtest
   #add_cxx_compiler_flag_if_supported(OUR_FLAGS_OWN "-Wuseless-cast")
-else()
-  if(TARGET_OS STREQUAL "haiku")
-    set(PLATFORM_CLIENT)
-    find_package(OpenGL)
-    set(PLATFORM_LIBS GL network)
-  endif()
 endif()
 
 if(NOT MSVC AND NOT HAIKU)
@@ -549,6 +545,12 @@ elseif(TARGET_OS STREQUAL "mac")
   )
   set(PLATFORM_CLIENT_LIBS ${COCOA} ${OPENGL})
   set(PLATFORM_LIBS ${CARBON} ${SECURITY})
+elseif(TARGET_OS STREQUAL "haiku")
+    set(PLATFORM_CLIENT)
+    find_package(OpenGL)
+    set(PLATFORM_LIBS GL network)
+    set(PLATFORM_CLIENT_LIBS ${OPENGL_gl_LIBRARY})
+    set(PLATFORM_CLIENT_INCLUDE_DIRS ${OPENGL_INCLUDE_DIR})
 else()
   find_package(Notify)
   find_package(OpenGL)