don't trigger rebuild on config.h.in

Lately I'm seeing unecessary rebuilds because config.h.in is newer than the
./configure file. The rule to trigger on *.in files is intended for "manual"
.in files, not those from autoconf/automake. Exclude config.h.in.

gen_makefile.py

@@ -167,7 +167,7 @@ def gen_make(proj, deps, configure_opts, jobs, make_dir, src_dir, build_dir, url
   return r'''
 ### {proj} ###
 
-{proj}_configure_files := $(shell find {src_proj} -name "Makefile.am" -or -name "*.in" -and -not -name "Makefile.in" )
+{proj}_configure_files := $(shell find {src_proj} -name "Makefile.am" -or -name "*.in" -and -not -name "Makefile.in" -and -not -name "config.h.in" )
 {proj}_files := $(shell find {src_proj} -name "*.[hc]" -or -name "*.py" -or -name "*.cpp" -or -name "*.tpl" -or -name "*.map")
 
 .make.{proj}.clone: