xsct-tc: append the local system's /usr/bin dir as Xvfb fallback

See changes to README.md.

Essentially, we need to fallback to locally found Xvfb and xlsclients
since the xserver-xorg recipe won't build without "x11" in
DISTRO_FEATURE.

Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Manjukumar Matha <manjukumar.harthikote-matha@xilinx.com>

README.md

@@ -22,7 +22,14 @@ Dependencies
 
 This layer depends on:
 
-XSCT being installed somewhere the yocto build can access. You must define
+* **If you don't have "x11" in your DISTRO_FEATURES, you'll need
+`xlsclients` and `Xvfb` to satisfy the SDK's dependence on it. You may install
+these by `apt-get install -y xvfb x11-utils` or the like. Note that if your
+system distro doesn't install those in /usr/bin, you'll need to provide links
+for them in /usr/bin since xsct (from the SDK itself) not only depends on these
+but it actually assumes /usr/bin.
+
+* XSCT being installed somewhere the yocto build can access. You must define
 this path by specifying the XILINX_SDK_TOOLCHAIN variable globally, typically
 in your local.conf (or site.conf).
 

classes/xsct-tc.bbclass

@@ -1,5 +1,6 @@
 XSCT_PATH_ADD = "${XILINX_SDK_TOOLCHAIN}/bin:"
 PATH =. "${XSCT_PATH_ADD}"
+PATH_append = ":/usr/bin"
 
 def xsct_run(d):
     import bb.process