build: generalize linking openal-soft to libfmt

Followup on the previous 3 commits to fix MSVC builds by linking libfmt
which openal-soft now needs.

Change the relevant CMake to link libfmt when it is found on all
platforms.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

src/wx/CMakeLists.txt

@@ -181,12 +181,10 @@ endif()
 # Find OpenAL (required).
 find_package(OpenAL REQUIRED)
 
-if(WIN32)
-    if(CMAKE_BUILD_TYPE STREQUAL "Debug")
-        find_library(FMT fmtd)
-    else()
-        find_library(FMT fmt)
-    endif()
+if(CMAKE_BUILD_TYPE STREQUAL "Debug")
+    find_library(FMT_LIBRARY NAMES fmtd fmt)
+else()
+    find_library(FMT_LIBRARY fmt)
 endif()
 
 # Workaround of static liblzma not being found on MSYS2.
@@ -283,8 +281,12 @@ function(configure_wx_target target)
     if(OPENAL_STATIC)
         _add_compile_definitions(AL_LIBTYPE_STATIC)
 
+        if(FMT_LIBRARY)
+            list(APPEND OPENAL_LIBRARY ${FMT_LIBRARY} avrt)
+        endif()
+
         if(WIN32)
-            list(APPEND OPENAL_LIBRARY ${FMT} avrt)
+            list(APPEND OPENAL_LIBRARY avrt)
         endif()
     endif()
     _add_include_directories(${OPENAL_INCLUDE_DIR})