crt: Add emulation of _set_doserrno() function for pre-msvcr80 import libs

Function _set_doserrno() is available in msvcr80+, UCRT and also in
msvcrt.dll since Windows Vista.

Signed-off-by: Martin Storsjö <martin@martin.st>

mingw-w64-crt/Makefile.am

diff --git a/mingw-w64-crt/Makefile.am b/mingw-w64-crt/Makefile.am
index a0546f4..a489470 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -563,6 +563,7 @@
   misc/_get_current_locale.c \
   misc/_get_doserrno.c \
   misc/_initterm_e.c \
+  misc/_set_doserrno.c \
   misc/_time64.c \
   misc/imaxabs.c \
   misc/lc_locale_func.c \
@@ -625,6 +626,7 @@
   misc/_get_current_locale.c \
   misc/_get_doserrno.c \
   misc/_initterm_e.c \
+  misc/_set_doserrno.c \
   misc/output_format.c \
   misc/_get_errno.c \
   misc/_set_errno.c \
@@ -895,6 +897,7 @@
   misc/_get_wpgmptr.c \
   misc/_initterm_e.c \
   misc/_recalloc.c \
+  misc/_set_doserrno.c \
   misc/_set_errno.c \
   misc/imaxabs.c \
   misc/invalid_parameter_handler.c \

mingw-w64-crt/lib-common/msvcrt.def.in

diff --git a/mingw-w64-crt/lib-common/msvcrt.def.in b/mingw-w64-crt/lib-common/msvcrt.def.in
index 05a59ba..ee7515c 100644
--- a/mingw-w64-crt/lib-common/msvcrt.def.in
+++ b/mingw-w64-crt/lib-common/msvcrt.def.in
@@ -1615,7 +1615,7 @@
 _searchenv_s
 F_I386(_seh_longjmp_unwind4@4)
 _set_controlfp
-_set_doserrno
+F_ARM_ANY(_set_doserrno) ; i386 and x64 _set_doserrno replaced by emu
 F_ARM_ANY(_set_errno) ; i386 and x64 _set_errno replaced by emu
 _set_fileinfo
 _set_fmode

mingw-w64-crt/misc/_set_doserrno.c

diff --git a/mingw-w64-crt/misc/_set_doserrno.c b/mingw-w64-crt/misc/_set_doserrno.c
new file mode 100644
index 0000000..5c51980
--- /dev/null
+++ b/mingw-w64-crt/misc/_set_doserrno.c
@@ -0,0 +1,13 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+#include <stdlib.h>
+
+errno_t __cdecl _set_doserrno(unsigned long value)
+{
+  _doserrno = value;
+  return 0;
+}
+errno_t (__cdecl *__MINGW_IMP_SYMBOL(_set_doserrno))(unsigned long) = _set_doserrno;