terminal.bbclass: Generate do_terminal as bitbake would

This changes the runfile that is generated to have the same behaviour as
bitbake with regards to emitting the shebang and trap code. The existing
implementation used 'env' with the current var-SHELL. This means that if
the user has configured there system/environment with a alternate shell
(e.g. csh, zsh, fish, etc.) the do_terminal function would attempt to
execute with the wrong/incompatible shell and fail silently.

With this change devshell and other classes that rely on terminal can
now run when the var-SHELL is not set to a sh compatible shell. For
devshell, it will launch the devshell with the users configured shell.

(From OE-Core rev: 53724281eb486847bc3be824aa4513a8688ec296)

Signed-off-by: Nathan Rossi <nathan@nathanrossi.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/terminal.bbclass

@@ -14,6 +14,7 @@ def oe_terminal_prioritized():
     return " ".join(o.name for o in oe.terminal.prioritized())
 
 def emit_terminal_func(command, envdata, d):
+    import bb.build
     cmd_func = 'do_terminal'
 
     envdata.setVar(cmd_func, 'exec ' + command)
@@ -25,8 +26,7 @@ def emit_terminal_func(command, envdata, d):
     bb.utils.mkdirhier(os.path.dirname(runfile))
 
     with open(runfile, 'w') as script:
-        script.write('#!/usr/bin/env %s\n' % d.getVar('SHELL'))
-        script.write('set -e\n')
+        script.write(bb.build.shell_trap_code())
         bb.data.emit_func(cmd_func, script, envdata)
         script.write(cmd_func)
         script.write("\n")