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

Function _get_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 b253201..a0546f4 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -561,6 +561,7 @@
   misc/_create_locale.c \
   misc/_free_locale.c \
   misc/_get_current_locale.c \
+  misc/_get_doserrno.c \
   misc/_initterm_e.c \
   misc/_time64.c \
   misc/imaxabs.c \
@@ -622,6 +623,7 @@
   misc/_create_locale.c \
   misc/_free_locale.c \
   misc/_get_current_locale.c \
+  misc/_get_doserrno.c \
   misc/_initterm_e.c \
   misc/output_format.c \
   misc/_get_errno.c \
@@ -884,6 +886,7 @@
   misc/_aligned_recalloc.c \
   misc/_configthreadlocale.c \
   misc/_get_daylight.c \
+  misc/_get_doserrno.c \
   misc/_get_dstbias.c \
   misc/_get_errno.c \
   misc/_get_pgmptr.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 2e696f9..05a59ba 100644
--- a/mingw-w64-crt/lib-common/msvcrt.def.in
+++ b/mingw-w64-crt/lib-common/msvcrt.def.in
@@ -1425,7 +1425,7 @@
 _fwscanf_l
 _fwscanf_s_l
 _gcvt_s
-_get_doserrno
+F_ARM_ANY(_get_doserrno) ; i386 and x64 _get_doserrno replaced by emu
 _get_environ
 F_ARM_ANY(_get_errno) ; i386 and x64 _get_errno replaced by emu
 _get_fileinfo

mingw-w64-crt/misc/_get_doserrno.c

diff --git a/mingw-w64-crt/misc/_get_doserrno.c b/mingw-w64-crt/misc/_get_doserrno.c
new file mode 100644
index 0000000..4abde0e
--- /dev/null
+++ b/mingw-w64-crt/misc/_get_doserrno.c
@@ -0,0 +1,20 @@
+/**
+ * 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>
+#include <errno.h>
+
+errno_t __cdecl _get_doserrno(unsigned long *value)
+{
+  if (!value)
+  {
+    errno = EINVAL;
+    return EINVAL;
+  }
+
+  *value = _doserrno;
+  return 0;
+}
+errno_t (__cdecl *__MINGW_IMP_SYMBOL(_get_doserrno))(unsigned long *) = _get_doserrno;