staging: Don't put ptest files into the sysroot

This wastes space/time as the ptest files aren't going to be used in the
sysroot so add them to the blacklist.

(From OE-Core rev: 61591fe2eea588ff92ff7f81f2ed8844617f5307)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/staging.bbclass

@@ -31,6 +31,7 @@ SYSROOT_DIRS_BLACKLIST = " \
     ${datadir}/applications \
     ${datadir}/fonts \
     ${datadir}/pixmaps \
+    ${libdir}/${PN}/ptest \
 "
 
 sysroot_stage_dir() {