Refactor build-aux entries in .gitignore

Author: hebasto

.gitignore

@@ -45,20 +45,9 @@ coverage.*.html
 *.gcno
 *.gcov
 
-build-aux/ar-lib
-build-aux/config.guess
-build-aux/config.sub
-build-aux/depcomp
-build-aux/install-sh
-build-aux/ltmain.sh
-build-aux/m4/libtool.m4
-build-aux/m4/lt~obsolete.m4
-build-aux/m4/ltoptions.m4
-build-aux/m4/ltsugar.m4
-build-aux/m4/ltversion.m4
-build-aux/missing
-build-aux/compile
-build-aux/test-driver
+/build-aux/*
+!/build-aux/m4/bitcoin_secp.m4
+
 libsecp256k1.pc
 
 ### CMake