cmake: Add option to pass flags not used for host tools

CMakeLists.txt

@@ -5,6 +5,7 @@ project(motis)
 set(CMAKE_POLICY_DEFAULT_CMP0077 NEW)
 
 option(MOTIS_MIMALLOC "use mimalloc" OFF)
+option(MOTIS_TARGET_FLAGS "Flags to use to build code that ends up in the resulting executable. They are not used for host tools." "")
 
 if (NOT DEFINED CMAKE_MSVC_RUNTIME_LIBRARY)
     if (MOTIS_MIMALLOC)
@@ -198,3 +199,9 @@ add_custom_target(motis-web-ui
         WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/ui"
         VERBATIM
 )
+
+foreach(t mimalloc adr osr nigiri gtfsrt
+        geo tiles tiles-import-library
+        motis motis-api motislib)
+    target_compile_options(${t} PUBLIC ${MOTIS_TARGET_FLAGS})
+endforeach()