win32 ngx_is_exec() stub

src/os/win32/ngx_files.h

diff --git a/src/os/win32/ngx_files.h b/src/os/win32/ngx_files.h
index adcaab3..e0fa700 100644
--- a/src/os/win32/ngx_files.h
+++ b/src/os/win32/ngx_files.h
@@ -104,6 +104,7 @@
 #define ngx_is_dir(fi)      ((fi)->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
 #define ngx_is_file(fi)     !((fi)->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
 #define ngx_is_link(fi)     0
+#define ngx_is_exec(fi)     0
 
 #define ngx_file_access(fi) 0