dbus: fix a hard dependency about dbus-ptest

If image contains dbus and ptest is in DISTRO_FEATURES, dbus-ptest package
is installed, regardless of whether ptest-pkgs is in IMAGE_FEATURES. This
issue will increase size for most small images.
This patch fixes this problem.

[YOCTO #5702]

(From OE-Core rev: 0416583f014138656babdf78a574357ae5ff25bd)

Signed-off-by: Chong Lu <Chong.Lu@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
gcc: Clean up configure_prepend and fix for mingw

The do_configure_prepend was duplicated in gcc-4.X.inc and
gcc-configure-common.inc leading to confusion when reading the resulting
do_configure task where the file was processed twice.

The only difference was the removal of the include line for gcc 4.8/4.9.

On mingw were were seeing two issues, firstly that the if statements meant
the values we wanted weren't being set, the second that the include
paths were still wrong as there was no header path set.

To fix the first issue, the #ifdef conditionals were removed, we want
to set these things unconditionally. The second issue is addressed by
setting the NATIVE_SYSTEM_HEADER_DIR variable here (it was already
set in t-oe).

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