How to pass flags to the compiler in separate linking step

[JohanEngelen]

Issue discussed here:
https://forum.dlang.org/post/[email protected]

When compilation and linking are separate:

• compilation step: dflags is passed to the compiler
• linking step: lflags is prefixed with -L and then passed to the compiler

How to pass a flag to the compiler during linking without the -L prefix?
This is needed for example for -flto=... and -fsanitize=... with LDC.

(note that separate linking is not implemented for LDC (#809), but it is possible when ldmd2 is used as is done in the forum thread)

[kinke]

Resolved by #1755 (for ldc2, not ldmd2): https://github.com/kinke/dub/blob/cfb281e289e7f72bfdd0f3e04407470d27cb8c4b/source/dub/compilers/ldc.d#L270-L288