remove dependency of version.h on .git/* to avoid errors

the wildcard function in GNU make includes dangling symlinks; if any
exist under the .git directory, they would get added as dependencies,
causing make to exit with an error due to lacking a rule to build the
missing file.

as far as I can tell, git operations which should force version.h to
be rebuilt must all touch the mtime of the top-level .git directory.
diff --git a/Makefile b/Makefile
index 69ab304..0ab0bfd 100644
--- a/Makefile
+++ b/Makefile
@@ -80,7 +80,7 @@
 include/bits/alltypes.h: include/bits/alltypes.h.in include/alltypes.h.in tools/mkalltypes.sed
 	sed -f tools/mkalltypes.sed include/bits/alltypes.h.in include/alltypes.h.in > $@
 
-src/internal/version.h: $(wildcard VERSION .git .git/*)
+src/internal/version.h: $(wildcard VERSION .git)
 	printf '#define VERSION "%s"\n' "$$(sh tools/version.sh)" > $@
 
 src/internal/version.lo: src/internal/version.h