devshell.bbclass: Allow running devshell and fakeroot together

Currently its hard to run a devshell complete with fakeroot context. This
patch allows the fakeroot flag on the task to do this, as with any other
task. Since we may need to start X terminal applications, we need to
only start the fakeroot session on the final command, hence the hoops
this code jumps through.

As always with fakeroot, you can break out and run a command without
the fake permissions with syntax like "PSEUDO_UNLOAD=1 <command>"

[YOCTO #3374]

(From OE-Core rev: 0a2662a48eaf0487db043c348e2834bb9cdd0466)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/devshell.bbclass

@@ -1,10 +1,27 @@
 inherit terminal
 
+DEVSHELL = "${SHELL}"
+
 python do_devshell () {
-    oe_terminal(d.getVar('SHELL', True), 'OpenEmbedded Developer Shell', d)
+    oe_terminal(d.getVar('DEVSHELL', True), 'OpenEmbedded Developer Shell', d)
 }
 
 addtask devshell after do_patch
 
 do_devshell[dirs] = "${S}"
 do_devshell[nostamp] = "1"
+
+# devshell and fakeroot/pseudo need careful handling since only the final
+# command should run under fakeroot emulation, any X connection should
+# be done as the normal user. We therfore carefully construct the envionment
+# manually
+python () {
+    if d.getVarFlag("do_devshell", "fakeroot"):
+       d.prependVar("DEVSHELL", "pseudo ")
+       fakeenv = d.getVar("FAKEROOTENV", True).split()
+       for f in fakeenv:
+            k = f.split("=")
+            d.setVar(k[0], k[1])           
+            d.appendVar("OE_TERMINAL_EXPORTS", " " + k[0])
+       d.delVarFlag("do_devshell", "fakeroot")
+}