CMake: fix try_compile and other checks for iOS build

build/cmake/toolkit.cmake

@@ -12,6 +12,10 @@ wx_option(wxUSE_GUI "Use GUI" ON)
 
 if(CMAKE_OSX_SYSROOT MATCHES iphoneos)
     set(IPHONE ON)
+
+    # workaround a bug where try_compile (and functions using it,
+    # like find_package, check_c_source_compiles) fails
+    set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 endif()
 
 if(WIN32)