Fix issue with B variable in bmcweb

When bmcweb is built with devtool, the B directory includes the trailing
slash, when it isn't devtooled (ie built normally) the B variable
doesn't include the slash.  This causes issues when enabling the bmcweb
ptest targets.

This commit adds the slash, to make it build in both cases

Tested:
built with:
DISTRO_FEATURES_append = " ptest"
CORE_IMAGE_EXTRA_INSTALL += "bmcweb-ptest"
in local.conf, with both:

devtool modify bmcweb
and
devtool reset bmcweb
and verified code now builds both ways.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ie8bbe598b3d165f038c1e4df09ca97e02aeb539a
diff --git a/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb b/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
index b26cec0..67378cf 100644
--- a/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
+++ b/meta-phosphor/recipes-phosphor/interfaces/bmcweb_git.bb
@@ -44,7 +44,7 @@
 
 do_install_ptest() {
         install -d ${D}${PTEST_PATH}/test
-        cp -rf ${B}*_test ${D}${PTEST_PATH}/test/
+        cp -rf ${B}/*_test ${D}${PTEST_PATH}/test/
 }
 
 FILES_${PN} += "${datadir}/** "