setarch: use a login shell; fixes #12066.

* This also updates /etc/profile to detect whether our
  parent process is a shell, and changes the banner
  message accordingly.
* Also, pipe errors to /dev/null, in case grep is not
  installed; this allows us to not require grep as a
  dependency, and let the banner message do the right
  thing.

data/etc/profile

@@ -3,7 +3,12 @@
 # Place user customizations in /.profile
 #
 
-echo -e "\nWelcome to the Haiku shell.\n"
+ps |& grep -e $PPID |& grep -e $SHELL |& grep -q -e $PPID > /dev/null 2>&1
+if [ $? -eq 1 ] ; then
+	echo -e "\nWelcome to the Haiku shell.\n"
+else
+	echo -e "\nSwitching to architecture `getarch`\n"
+fi
 
 export USER=`id -un`
 export GROUP=`id -gn`

src/bin/setarch.cpp

@@ -237,13 +237,14 @@ main(int argc, const char* const* argv)
 	}
 
 	// if no command is given, get the user's shell
-	const char* shellCommand[2];
+	const char* shellCommand[3];
 	if (commandArgs == NULL) {
 		struct passwd* pwd = getpwuid(geteuid());
 		shellCommand[0] = pwd != NULL ? pwd->pw_shell : "/bin/sh";
-		shellCommand[1] = NULL;
+		shellCommand[1] = "-l";
+		shellCommand[2] = NULL;
 		commandArgs = shellCommand;
-		commandArgCount = 1;
+		commandArgCount = 2;
 	}
 
 	// exec the command