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

Function _get_timezone() is available in msvcr80+ and UCRT.

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 924a90c..23962a6 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -334,6 +334,7 @@
   misc/_configthreadlocale.c \
   misc/_get_daylight.c \
   misc/_get_dstbias.c \
+  misc/_get_timezone.c \
   misc/_recalloc.c \
   misc/_set_purecall_handler.c \
   misc/imaxdiv.c \
@@ -882,6 +883,7 @@
   misc/_get_daylight.c \
   misc/_get_dstbias.c \
   misc/_get_errno.c \
+  misc/_get_timezone.c \
   misc/_initterm_e.c \
   misc/_recalloc.c \
   misc/_set_errno.c \

mingw-w64-crt/misc/_get_timezone.c

diff --git a/mingw-w64-crt/misc/_get_timezone.c b/mingw-w64-crt/misc/_get_timezone.c
new file mode 100644
index 0000000..40dce33
--- /dev/null
+++ b/mingw-w64-crt/misc/_get_timezone.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 <time.h>
+#include <errno.h>
+
+errno_t __cdecl _get_timezone(long *value)
+{
+  if (!value)
+  {
+    errno = EINVAL;
+    return EINVAL;
+  }
+
+  *value = _timezone;
+  return 0;
+}
+errno_t (__cdecl *__MINGW_IMP_SYMBOL(_get_timezone))(long *) = _get_timezone;