patch 8.0.0450: v:progpath is not reliably set
Problem: v:progpath is not reliably set.
Solution: Read /proc/self/exe if possible. (idea by Michal Grochmal)
Also fixes missing #if.
diff --git a/src/config.h.in b/src/config.h.in
index 49ed596..a9bcf1e 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -446,6 +446,9 @@
/* Define if fcntl()'s F_SETFD command knows about FD_CLOEXEC */
#undef HAVE_FD_CLOEXEC
+/* Define if /proc/self/exe can be read */
+#undef HAVE_PROC_SELF_EXE
+
/* Define if you want Cygwin to use the WIN32 clipboard, not compatible with X11*/
#undef FEAT_CYGWIN_WIN32_CLIPBOARD