Choose the correct startup object for mingw-w64

If -municode is passed to mingw-w64's gcc, then crt2u.o (which causes
wmain to be selected) should be linked rather than crt2.o. In passing,
the code now sniffs for -nostartfiles, which causes neither crt2.o nor
crt2u.o to be considered.

Author: dra27

CHANGES

@@ -30,6 +30,8 @@ Version 0.44
   as querying the compilers for their library search paths. Support parsing
   clang output.
   (Antonin Décimo, review by David Allsopp)
+- GPR#146: For mingw-w64, select crt2u.o instead of crt2.o if -link -municode
+  is specified (David Allsopp)
 
 Version 0.43
 - GPR#108: Add -lgcc_s to Cygwin's link libraries, upstreaming a patch from the

reloc.ml

@@ -1423,8 +1423,14 @@ let setup_toolchain () =
       with Not_found -> ()
     in
     default_libs := "-lmingw32" :: "-lgcc" :: !default_libs;
-    if !exe_mode = `EXE then default_libs := "crt2.o" :: !default_libs
-    else default_libs := "dllcrt2.o" :: !default_libs
+    if not (List.mem "-nostartfiles" !extra_args) then begin
+      if !exe_mode = `EXE then
+        if List.mem "-municode" !extra_args then
+          default_libs := "crt2u.o" :: !default_libs
+        else
+          default_libs := "crt2.o" :: !default_libs
+      else default_libs := "dllcrt2.o" :: !default_libs
+    end
   in
   match !toolchain with
   | _ when !builtin_linker ->