I’m using a version of gcc that requires a –sysroot flag for all invocations. This includes invocations for assembling .S files in the context lib. Looking at gcc.jam, I see that there is no $(USER_OPTIONS) parameter passed. I tried mimicking the msvc.jam mechanism that specifies <asmflags> as USER_ASMFLAGS, but as my knowledge of bjam is virtually nil I have not been successful.
Can someone provide a pointer or a suggestion as to what to do?