gitignore: ignore build*/ entirely

Previously parts of build*/ were ignored, but unless you committed the top-level
build/ in a branch this didn't achieve anything.  Change that to ignore all
top-level build* directories.

(From OE-Core rev: 6e3353872d377dfe2689832b3f04f18c2366bc8c)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

.gitignore

@@ -2,11 +2,7 @@ bitbake
 *.pyc
 *.pyo
 /*.patch
-build*/conf/local.conf
-build*/conf/bblayers.conf
-build*/downloads
-build*/tmp/
-build*/sstate-cache
+build*/
 pyshtables.py
 pstage/
 scripts/oe-git-proxy-socks