fix Makefile creation to not pick up files ending in .v in .git

If one names a branch "something-something-file.v", then the current
script will find it in the .git directory and try to compile git's
branch description as a Coq file...

create_makefile.sh

@@ -10,7 +10,7 @@ fi
 
 # Compile all *.v files (except the ones that define the decidable equality). Those
 # are directly included in other files.
-coq_makefile -f _CoqProject $(find . -name "*.v" ! -name "*#*" ! -name "*eqdec*.v" -print) -o Makefile
+coq_makefile -f _CoqProject $(find . -name "*.v"  ! -name "*#*" ! -name "*eqdec*.v" ! -path "./.git/*" -print) -o Makefile
 
 # Fix the 'make validate' command. It doesn't handle the library prefix properly
 # and cause clashes for files with the same name. This forces full filenames and