Fixed Windows/MSVC compilation.

LibConf

@@ -13,7 +13,10 @@ mijin_sources = Split("""
     source/mijin/virtual_filesystem/stacked.cpp
 """)
 
-lib_libbacktrace = env.Cook('libbacktrace')
+dependencies = []
+if env['COMPILER_FAMILY'] in ('gcc', 'clang'):
+	lib_libbacktrace = env.Cook('libbacktrace')
+	dependencies.append(lib_libbacktrace)
 
 cppdefines = []
 if env['BUILD_TYPE'] == 'debug':
@@ -23,7 +26,7 @@ if env['BUILD_TYPE'] == 'debug':
 lib_mijin = env.UnityStaticLibrary(
     target = env['LIB_DIR']  + '/mijin',
     source = mijin_sources,
-    dependencies = [lib_libbacktrace],
+    dependencies = dependencies,
     CPPDEFINES = list(env['CPPDEFINES']) + cppdefines
 )