Fix MSVC permissive flags (#123)

Fixes #122.

Author: TheLartians

CMakeLists.txt

@@ -49,7 +49,7 @@ add_library(Greeter ${headers} ${sources})
 set_target_properties(Greeter PROPERTIES CXX_STANDARD 17)
 
 # being a cross-platform target, we enforce standards conformance on MSVC
-target_compile_options(Greeter PUBLIC "$<$<COMPILE_LANG_AND_ID:CXX,MSVC>:/permissive>")
+target_compile_options(Greeter PUBLIC "$<$<COMPILE_LANG_AND_ID:CXX,MSVC>:/permissive->")
 
 # Link dependencies
 target_link_libraries(Greeter PRIVATE fmt::fmt)