[mingw-filesystem/f17] (4 commits) ...Generate the DLL name provides from mingw-crt import libraries

[epienbro]

Summary of changes:

  f14297d... Simplify the %mingw_make_install macro (*)
  3fc8958... Fix warnings during debuginfo generation (*)
  9dad08a... Define mingw_build_win32/win64 in system macros (*)
  e66c6cc... Generate the DLL name provides from mingw-crt import librar (*)

(*) This commit already existed in another branch; no separate mail sent